STL源码剖析——STL算法之find查找算法

柔情只为你懂 2022-08-12 19:28 257阅读 0赞

## 前言 ##

由于在前文的《[STL算法剖析][STL]》中，源码剖析非常多，不方便学习，也不方便以后复习，这里把这些算法进行归类，对他们单独的源码剖析进行讲解。本文介绍的STL算法中的find、search查找算法。在STL源码中有关算法的函数大部分在本文介绍，包含findand find\_if、adjacent\_find、search、search\_n、lower\_bound、 upper\_bound、 equal\_range、binary\_search、find\_first\_of、find\_end相关算法，下面对这些算法的源码进行了详细的剖析，并且适当给出应用例子，增加我们对其理解，方便我们使用这些算法。具体详见下面源码剖析。

## 查找算法源码剖析 ##

// find and find_if.
    //查找区间[first,last)内元素第一个与value值相等的元素，并返回其位置
    //其中find函数是采用默认的equality操作operator==
    //find_if是采用用户自行指定的操作pred
    
    //若find函数萃取出来的迭代器类型为输入迭代器input_iterator_tag，则调用此函数
    template <class _InputIter, class _Tp>
    inline _InputIter find(_InputIter __first, _InputIter __last,
                           const _Tp& __val,
                           input_iterator_tag)
    {//若尚未到达区间的尾端，且未找到匹配的值，则继续查找
      while (__first != __last && !(*__first == __val))
        ++__first;
      //若找到匹配的值，则返回该位置
      //若找不到，即到达区间尾端，此时first=last，则返回first
      return __first;
    }
    //若find_if函数萃取出来的迭代器类型为输入迭代器input_iterator_tag，则调用此函数
    template <class _InputIter, class _Predicate>
    inline _InputIter find_if(_InputIter __first, _InputIter __last,
                              _Predicate __pred,
                              input_iterator_tag)
    {//若尚未到达区间的尾端，且未找到匹配的值，则继续查找
      while (__first != __last && !__pred(*__first))
        ++__first;
      //若找到匹配的值，则返回该位置
      //若找不到，即到达区间尾端，此时first=last，则返回first
      return __first;
    }
    
    #ifdef __STL_CLASS_PARTIAL_SPECIALIZATION
    //若find函数萃取出来的迭代器类型为随机访问迭代器random_access_iterator_tag，则调用此函数
    template <class _RandomAccessIter, class _Tp>
    _RandomAccessIter find(_RandomAccessIter __first, _RandomAccessIter __last,
                           const _Tp& __val,
                           random_access_iterator_tag)
    {
      typename iterator_traits<_RandomAccessIter>::difference_type __trip_count
        = (__last - __first) >> 2;
    
      for ( ; __trip_count > 0 ; --__trip_count) {
        if (*__first == __val) return __first;
        ++__first;
    
        if (*__first == __val) return __first;
        ++__first;
    
        if (*__first == __val) return __first;
        ++__first;
    
        if (*__first == __val) return __first;
        ++__first;
      }
    
      switch(__last - __first) {
      case 3:
        if (*__first == __val) return __first;
        ++__first;
      case 2:
        if (*__first == __val) return __first;
        ++__first;
      case 1:
        if (*__first == __val) return __first;
        ++__first;
      case 0:
      default:
        return __last;
      }
    }
    //若find_if函数萃取出来的迭代器类型为随机访问迭代器random_access_iterator_tag，则调用此函数
    template <class _RandomAccessIter, class _Predicate>
    _RandomAccessIter find_if(_RandomAccessIter __first, _RandomAccessIter __last,
                              _Predicate __pred,
                              random_access_iterator_tag)
    {
      typename iterator_traits<_RandomAccessIter>::difference_type __trip_count
        = (__last - __first) >> 2;
    
      for ( ; __trip_count > 0 ; --__trip_count) {
        if (__pred(*__first)) return __first;
        ++__first;
    
        if (__pred(*__first)) return __first;
        ++__first;
    
        if (__pred(*__first)) return __first;
        ++__first;
    
        if (__pred(*__first)) return __first;
        ++__first;
      }
    
      switch(__last - __first) {
      case 3:
        if (__pred(*__first)) return __first;
        ++__first;
      case 2:
        if (__pred(*__first)) return __first;
        ++__first;
      case 1:
        if (__pred(*__first)) return __first;
        ++__first;
      case 0:
      default:
        return __last;
      }
    }
    
    #endif /* __STL_CLASS_PARTIAL_SPECIALIZATION */
    /*find函数功能：Returns an iterator to the first element in the range [first,last) that compares equal to val. 
    If no such element is found, the function returns last.
    find函数原型：
    	template <class InputIterator, class T>
    	InputIterator find (InputIterator first, InputIterator last, const T& val);
    */
    //find函数对外接口
    template <class _InputIter, class _Tp>
    inline _InputIter find(_InputIter __first, _InputIter __last,
                           const _Tp& __val)
    {
      __STL_REQUIRES(_InputIter, _InputIterator);
      __STL_REQUIRES_BINARY_OP(_OP_EQUAL, bool, 
                typename iterator_traits<_InputIter>::value_type, _Tp);
      //首先萃取出first迭代器的类型，根据迭代器的类型调用不同的函数
      return find(__first, __last, __val, __ITERATOR_CATEGORY(__first));
    }
    /*find_if函数功能：Returns an iterator to the first element in the range [first,last) for which pred returns true. 
    If no such element is found, the function returns last.
    find_if函数原型：
    	template <class InputIterator, class UnaryPredicate>
    	InputIterator find_if (InputIterator first, InputIterator last, UnaryPredicate pred);
    */
    //find_if 函数对外接口
    template <class _InputIter, class _Predicate>
    inline _InputIter find_if(_InputIter __first, _InputIter __last,
                              _Predicate __pred) {
      __STL_REQUIRES(_InputIter, _InputIterator);
      __STL_UNARY_FUNCTION_CHECK(_Predicate, bool,
              typename iterator_traits<_InputIter>::value_type);
      //首先萃取出first迭代器的类型，根据迭代器的类型调用不同的函数
      return find_if(__first, __last, __pred, __ITERATOR_CATEGORY(__first));
    }
    //find和find_if函数举例：
    /*
    	#include <iostream>     // std::cout
    	#include <algorithm>    // std::find_if
    	#include <vector>       // std::vector
    
    	bool IsOdd (int i) {
    	  return ((i%2)==1);
    	}
    
    	int main () {
    	  std::vector<int> myvector;
    
    	  myvector.push_back(10);
    	  myvector.push_back(25);
    	  myvector.push_back(40);
    	  myvector.push_back(55);
    
    	  std::vector<int>::iterator it = std::find_if (myvector.begin(), myvector.end(), IsOdd);
    	  std::cout << "The first odd value is " << *it << '\n';
    
    	  // using std::find with vector and iterator:
    	  it = find (myvector.begin(), myvector.end(), 40);
    	  if (it != myvector.end())
    		std::cout << "Element found in myvector: " << *it << '\n';
    	  else
    		std::cout << "Element not found in myints\n";
    
    	  return 0;
    	}
    	Output:
    	The first odd value is 25
    	Element found in myvector: 40
     
    */
    
    // adjacent_find.
    
    //查找区间[first,last)内第一次重复的相邻元素
    //若存在返回相邻元素的第一个元素位置
    //若不存在返回last位置
    /*该函数有两个版本：第一版本是默认操作operator==；第二版本是用户指定的二元操作pred
    函数对外接口的原型：
    equality (1)：默认操作是operator==
    	template <class ForwardIterator>
    	ForwardIterator adjacent_find (ForwardIterator first, ForwardIterator last);
    predicate (2)：用户指定的二元操作pred	
    	template <class ForwardIterator, class BinaryPredicate>
    	ForwardIterator adjacent_find (ForwardIterator first, ForwardIterator last,
                                      BinaryPredicate pred);
    
    */
    //版本一：默认操作是operator==
    template <class _ForwardIter>
    _ForwardIter adjacent_find(_ForwardIter __first, _ForwardIter __last) {
      __STL_REQUIRES(_ForwardIter, _ForwardIterator);
      __STL_REQUIRES(typename iterator_traits<_ForwardIter>::value_type,
                     _EqualityComparable);
      /*
      情况1：若输入区间为空，则直接返回尾端last；
      情况2：若输入区间不为空，且存在相邻重复元素，则返回相邻元素的第一个元素的位置；
      情况3：若输入区间不为空，但是不存在相邻重复元素，则直接返回尾端last；
      */
      //情况1：
      if (__first == __last)//若输入区间为空
        return __last;//直接返回last
      //情况2：
      _ForwardIter __next = __first;//定义当前位置的下一个位置(即当前元素的相邻元素)
      while(++__next != __last) {//若还没到达尾端，执行while循环
        if (*__first == *__next)//相邻元素值相等，则找到相邻重复元素
          return __first;//返回第一个元素的位置
        __first = __next;//若暂时找不到，则继续找，直到到达区间尾端
      }
      //情况3：
      return __last;//直接返回尾端last
    }
    
    //版本二：用户指定的二元操作pred	
    //实现过程和版本一一样，只是判断规则不同
    template <class _ForwardIter, class _BinaryPredicate>
    _ForwardIter adjacent_find(_ForwardIter __first, _ForwardIter __last,
                               _BinaryPredicate __binary_pred) {
      __STL_REQUIRES(_ForwardIter, _ForwardIterator);
      __STL_BINARY_FUNCTION_CHECK(_BinaryPredicate, bool,
              typename iterator_traits<_ForwardIter>::value_type,
              typename iterator_traits<_ForwardIter>::value_type);
      if (__first == __last)
        return __last;
      _ForwardIter __next = __first;
      while(++__next != __last) {
    	  //如果找到相邻元素符合用户指定条件，就返回第一元素位置
        if (__binary_pred(*__first, *__next))
          return __first;
        __first = __next;
      }
      return __last;
    }
    //adjacent_find函数举例：
    /*
    	#include <iostream>     // std::cout
    	#include <algorithm>    // std::adjacent_find
    	#include <vector>       // std::vector
    
    	bool myfunction (int i, int j) {
    	  return (i==j);
    	}
    
    	int main () {
    	  int myints[] = {5,20,5,30,30,20,10,10,20};
    	  std::vector<int> myvector (myints,myints+8);
    	  std::vector<int>::iterator it;
    
    	  // using default comparison:
    	  it = std::adjacent_find (myvector.begin(), myvector.end());
    
    	  if (it!=myvector.end())
    		std::cout << "the first pair of repeated elements are: " << *it << '\n';
    
    	  //using predicate comparison:
    	  it = std::adjacent_find (++it, myvector.end(), myfunction);
    
    	  if (it!=myvector.end())
    		std::cout << "the second pair of repeated elements are: " << *it << '\n';
    
    	  return 0;
    	}
    	Output:
    	the first pair of repeated elements are: 30
    	the second pair of repeated elements are: 10
    
    */
    
    
    // search.
    //在序列一[first1,last1)所涵盖的区间中，查找序列二[first2,last2)的首次出现点
    //该查找函数有两个版本：
    //版本一：使用默认的equality操作operator==
    //版本二：用户根据需要自行指定操作规则
    /*search函数功能：Searches the range [first1,last1) for the first occurrence of the sequence defined by [first2,last2), 
    and returns an iterator to its first element, or last1 if no occurrences are found.
    
    search函数的原型：
    equality (1)：版本一
    	template <class ForwardIterator1, class ForwardIterator2>
    	ForwardIterator1 search (ForwardIterator1 first1, ForwardIterator1 last1,
                                ForwardIterator2 first2, ForwardIterator2 last2);
    predicate (2)：版本二	
    	template <class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
    	ForwardIterator1 search (ForwardIterator1 first1, ForwardIterator1 last1,
                                ForwardIterator2 first2, ForwardIterator2 last2,
                                BinaryPredicate pred);
    */
    //版本一：使用默认的equality操作operator==
    template <class _ForwardIter1, class _ForwardIter2>
    _ForwardIter1 search(_ForwardIter1 __first1, _ForwardIter1 __last1,
                         _ForwardIter2 __first2, _ForwardIter2 __last2) 
    {
      __STL_REQUIRES(_ForwardIter1, _ForwardIterator);
      __STL_REQUIRES(_ForwardIter2, _ForwardIterator);
      __STL_REQUIRES_BINARY_OP(_OP_EQUAL, bool,
       typename iterator_traits<_ForwardIter1>::value_type,
       typename iterator_traits<_ForwardIter2>::value_type);
    
      // Test for empty ranges
      if (__first1 == __last1 || __first2 == __last2)
        return __first1;
    
      // Test for a pattern of length 1.
      _ForwardIter2 __tmp(__first2);
      ++__tmp;
      if (__tmp == __last2)
        return find(__first1, __last1, *__first2);
    
      // General case.
    
      _ForwardIter2 __p1, __p;
    
      __p1 = __first2; ++__p1;
    
      _ForwardIter1 __current = __first1;
    
      while (__first1 != __last1) {//若还没到达区间尾端
        __first1 = find(__first1, __last1, *__first2);//查找*first2在区间[first1,last1)首次出现的位置
        if (__first1 == __last1)//若在[first1,last1)中不存在*first2，即在[first1,last1)不存在子序列[first2,last2)
          return __last1;//则直接返回区间尾端
    
        __p = __p1;
        __current = __first1; 
        if (++__current == __last1)//若[first1,last1)只有一个元素，即序列[first1,last1)小于序列[first2,last2)
          return __last1;//不可能成为其子序列，返回last1
    
        while (*__current == *__p) {//若两个序列相对应的值相同
          if (++__p == __last2)//若序列[first2,last2)只有两个元素，且与序列一匹配
            return __first1;//则返回匹配的首次位置
          if (++__current == __last1)//若第一个序列小于第二个序列
            return __last1;//返回last1
        }
    
        ++__first1;
      }
      return __first1;
    }
    
    //版本二：用户根据需要自行指定操作规则
    template <class _ForwardIter1, class _ForwardIter2, class _BinaryPred>
    _ForwardIter1 search(_ForwardIter1 __first1, _ForwardIter1 __last1,
                         _ForwardIter2 __first2, _ForwardIter2 __last2,
                         _BinaryPred  __predicate) 
    {
      __STL_REQUIRES(_ForwardIter1, _ForwardIterator);
      __STL_REQUIRES(_ForwardIter2, _ForwardIterator);
      __STL_BINARY_FUNCTION_CHECK(_BinaryPred, bool,
       typename iterator_traits<_ForwardIter1>::value_type,
       typename iterator_traits<_ForwardIter2>::value_type);
    
      // Test for empty ranges
      if (__first1 == __last1 || __first2 == __last2)
        return __first1;
    
      // Test for a pattern of length 1.
      _ForwardIter2 __tmp(__first2);
      ++__tmp;
      if (__tmp == __last2) {
        while (__first1 != __last1 && !__predicate(*__first1, *__first2))
          ++__first1;
        return __first1;    
      }
    
      // General case.
    
      _ForwardIter2 __p1, __p;
    
      __p1 = __first2; ++__p1;
    
      _ForwardIter1 __current = __first1;
    
      while (__first1 != __last1) {
        while (__first1 != __last1) {
          if (__predicate(*__first1, *__first2))
            break;
          ++__first1;
        }
        while (__first1 != __last1 && !__predicate(*__first1, *__first2))
          ++__first1;
        if (__first1 == __last1)
          return __last1;
    
        __p = __p1;
        __current = __first1; 
        if (++__current == __last1) return __last1;
    
        while (__predicate(*__current, *__p)) {
          if (++__p == __last2)
            return __first1;
          if (++__current == __last1)
            return __last1;
        }
    
        ++__first1;
      }
      return __first1;
    }
    
    // search_n.  Search for __count consecutive copies of __val.
    //在序列[first,last)查找连续count个符合条件值value元素的位置
    //该查找函数有两个版本：
    //版本一：使用默认的equality操作operator==
    //版本二：用户根据需要自行指定操作规则
    /*search_n函数功能：Searches the range [first,last) for a sequence of count elements, 
    each comparing equal to val (or for which pred returns true).
    
    
    search_n函数的原型：
    equality (1)：版本一	
    	template <class ForwardIterator, class Size, class T>
    	ForwardIterator search_n (ForwardIterator first, ForwardIterator last,
                                 Size count, const T& val);
    predicate (2)：版本二	
    	template <class ForwardIterator, class Size, class T, class BinaryPredicate>
    	ForwardIterator search_n ( ForwardIterator first, ForwardIterator last,
                                  Size count, const T& val, BinaryPredicate pred );
    */
    //版本一：使用默认的equality操作operator==
    template <class _ForwardIter, class _Integer, class _Tp>
    _ForwardIter search_n(_ForwardIter __first, _ForwardIter __last,
                          _Integer __count, const _Tp& __val) {
      __STL_REQUIRES(_ForwardIter, _ForwardIterator);
      __STL_REQUIRES(typename iterator_traits<_ForwardIter>::value_type,
                     _EqualityComparable);
      __STL_REQUIRES(_Tp, _EqualityComparable);
    
      if (__count <= 0)
        return __first;
      else {//首先查找value第一次出现的位置
        __first = find(__first, __last, __val);
        while (__first != __last) {//若出现的位置不是区间尾端
          _Integer __n = __count - 1;//更新个数，下面只需查找n=count-1个连续相同value即可
          _ForwardIter __i = __first;
          ++__i;//从当前位置的下一个位置开始查找
    	  //若没有到达区间尾端，且个数n大于0，且区间元素与value值相等
          while (__i != __last && __n != 0 && *__i == __val) {
            ++__i;//继续查找
            --__n;//减少查找的次数，因为已经找到value再次出现
          }
          if (__n == 0)//若区间尚未到达尾端，但是count个value已经查找到
            return __first;//则输出查找到的首次出现value的位置
          else
            __first = find(__i, __last, __val);//若尚未找到连续count个value值的位置，则找出value下次出现的位置，并准备下一次while循环
        }
        return __last;
      }
    }
    //版本二：用户根据需要自行指定操作规则
    template <class _ForwardIter, class _Integer, class _Tp, class _BinaryPred>
    _ForwardIter search_n(_ForwardIter __first, _ForwardIter __last,
                          _Integer __count, const _Tp& __val,
                          _BinaryPred __binary_pred) {
      __STL_REQUIRES(_ForwardIter, _ForwardIterator);
      __STL_BINARY_FUNCTION_CHECK(_BinaryPred, bool, 
                 typename iterator_traits<_ForwardIter>::value_type, _Tp);
      if (__count <= 0)
        return __first;
      else {
        while (__first != __last) {
          if (__binary_pred(*__first, __val))
            break;
          ++__first;
        }
        while (__first != __last) {
          _Integer __n = __count - 1;
          _ForwardIter __i = __first;
          ++__i;
          while (__i != __last && __n != 0 && __binary_pred(*__i, __val)) {
            ++__i;
            --__n;
          }
          if (__n == 0)
            return __first;
          else {
            while (__i != __last) {
              if (__binary_pred(*__i, __val))
                break;
              ++__i;
            }
            __first = __i;
          }
        }
        return __last;
      }
    } 
    //search和search_n函数举例：
    /*
    	#include <iostream>     // std::cout
    	#include <algorithm>    // std::search_n
    	#include <vector>       // std::vector
    
    	bool mypredicate (int i, int j) {
    	  return (i==j);
    	}
    
    	int main () {
    	  int myints[]={10,20,30,30,20,10,10,20};
    	  std::vector<int> myvector (myints,myints+8);
    	  std::vector<int>::iterator it;
    
    	  // using default comparison:
    	  it = std::search_n (myvector.begin(), myvector.end(), 2, 30);
    	  if (it!=myvector.end())
    		std::cout << "two 30s found at position " << (it-myvector.begin()) << '\n';
    	  else
    		std::cout << "match not found\n";
    
    	  // using predicate comparison:
    	  it = std::search_n (myvector.begin(), myvector.end(), 2, 10, mypredicate);
    	  if (it!=myvector.end())
    		std::cout << "two 10s found at position " << int(it-myvector.begin()) << '\n';
    	  else
    		std::cout << "match not found\n";
        
    	  int needle1[] = {10,20};
      
    	  // using default comparison:
    	  it = std::search (myvector.begin(), myvector.end(), needle1, needle1+2);  
    	   if (it!=myvector.end())
    		std::cout << "needle1 found at position " << (it-myvector.begin()) << '\n';
    	  else
    		std::cout << "needle1 not found\n";
        
    	  // using predicate comparison:
    	  int needle2[] = {30,20,10};
    	  it = std::search (myvector.begin(), myvector.end(), needle2, needle2+3, mypredicate);
    	  if (it!=myvector.end())
    		std::cout << "needle2 found at position " << (it-myvector.begin()) << '\n';
    	  else
    		std::cout << "needle2 not found\n";
    
    	  return 0;
    	}
    	Output:
    	two 30s found at position 2
    	two 10s found at position 5
    	needle1 found at position 0
    	needle2 found at position 3
    */
    
    // Binary search (lower_bound, upper_bound, equal_range, binary_search).
    
    template <class _ForwardIter, class _Tp, class _Distance>
    _ForwardIter __lower_bound(_ForwardIter __first, _ForwardIter __last,
                               const _Tp& __val, _Distance*) 
    {
      _Distance __len = 0;
      distance(__first, __last, __len);//求取整个区间的长度len
      _Distance __half;
      _ForwardIter __middle;//定义区间的中间迭代器
    
      while (__len > 0) {//若区间不为空，则在区间[first,last)开始查找value值
        __half = __len >> 1;//向右移一位，相当于除以2，即取区间的中间值
        __middle = __first;//middle初始化为区间的起始位置
        advance(__middle, __half);//middle向后移half位，此时middle为区间的中间值
        if (*__middle < __val) {//将value值与中间值比较，即是二分查找,若中间值小于value，则继续查找右半部分
    		//下面两行令first指向middle的下一个位置
          __first = __middle;
          ++__first;
          __len = __len - __half - 1;//调整查找区间的长度
        }
        else
          __len = __half;//否则查找左半部分
      }
      return __first;
    }
    //在已排序区间[first,last)查找value值
    //若该区间存在与value相等的元素，则返回指向第一个与value相等的迭代器
    //若该区间不存在与value相等的元素，则返回指向第一个不小于value值的迭代器
    //若该区间的任何元素都比value值小，则返回last
    /*
    函数功能：Returns an iterator pointing to the first element in the range [first,last) which does not compare less than val.
    函数原型：
    default (1)	：版本一采用operator<比较
    	template <class ForwardIterator, class T>
    	ForwardIterator lower_bound (ForwardIterator first, ForwardIterator last,
                                   const T& val);
    custom (2)	：版本二采用仿函数comp比较规则
    	template <class ForwardIterator, class T, class Compare>
    	ForwardIterator lower_bound (ForwardIterator first, ForwardIterator last,
                                   const T& val, Compare comp);
    */
    //版本一
    template <class _ForwardIter, class _Tp>
    inline _ForwardIter lower_bound(_ForwardIter __first, _ForwardIter __last,
    				const _Tp& __val) {
      __STL_REQUIRES(_ForwardIter, _ForwardIterator);
      __STL_REQUIRES_SAME_TYPE(_Tp,
          typename iterator_traits<_ForwardIter>::value_type);
      __STL_REQUIRES(_Tp, _LessThanComparable);
      return __lower_bound(__first, __last, __val,
                           __DISTANCE_TYPE(__first));
    }
    
    template <class _ForwardIter, class _Tp, class _Compare, class _Distance>
    _ForwardIter __lower_bound(_ForwardIter __first, _ForwardIter __last,
                                  const _Tp& __val, _Compare __comp, _Distance*)
    {
      _Distance __len = 0;
      distance(__first, __last, __len);//求取整个区间的长度len
      _Distance __half;
      _ForwardIter __middle;//定义区间的中间迭代器
    
      while (__len > 0) {//若区间不为空，则在区间[first,last)开始查找value值
        __half = __len >> 1;//向右移一位，相当于除以2，即取区间的中间值
        __middle = __first;//middle初始化为区间的起始位置
        advance(__middle, __half);//middle向后移half位，此时middle为区间的中间值
        if (__comp(*__middle, __val)) {//若comp判断为true，则继续在右半部分查找
    		//下面两行令first指向middle的下一个位置
          __first = __middle;
          ++__first;
          __len = __len - __half - 1;//调整查找区间的长度
        }
        else
          __len = __half;//否则查找左半部分
      }
      return __first;
    }
    //版本二：
    template <class _ForwardIter, class _Tp, class _Compare>
    inline _ForwardIter lower_bound(_ForwardIter __first, _ForwardIter __last,
                                    const _Tp& __val, _Compare __comp) {
      __STL_REQUIRES(_ForwardIter, _ForwardIterator);
      __STL_REQUIRES_SAME_TYPE(_Tp,
          typename iterator_traits<_ForwardIter>::value_type);
      __STL_BINARY_FUNCTION_CHECK(_Compare, bool, _Tp, _Tp);
      return __lower_bound(__first, __last, __val, __comp,
                           __DISTANCE_TYPE(__first));
    }
    
    template <class _ForwardIter, class _Tp, class _Distance>
    _ForwardIter __upper_bound(_ForwardIter __first, _ForwardIter __last,
                               const _Tp& __val, _Distance*)
    {
      _Distance __len = 0;
      distance(__first, __last, __len);//求取整个区间的长度len
      _Distance __half;
      _ForwardIter __middle;//定义区间的中间迭代器
    
      while (__len > 0) {//若区间不为空，则在区间[first,last)开始查找value值
        __half = __len >> 1;//向右移一位，相当于除以2，即取区间的中间值
        __middle = __first;//middle初始化为区间的起始位置
        advance(__middle, __half);//middle向后移half位，此时middle为区间的中间值
        if (__val < *__middle)//若value小于中间元素值
          __len = __half;//查找左半部分
        else {
    		//下面两行令first指向middle的下一个位置
          __first = __middle;
          ++__first;
          __len = __len - __half - 1;//更新len的值
        }
      }
      return __first;
    }
    //在已排序区间[first,last)查找value值
    //返回大于value值的第一个元素的迭代器
    /*
    函数功能：Returns an iterator pointing to the first element in the range [first,last) which compares greater than val.
    函数原型：
    default (1)	：版本一采用operator<比较
    	template <class ForwardIterator, class T>
    	ForwardIterator upper_bound (ForwardIterator first, ForwardIterator last,
                                   const T& val);
    custom (2)	：版本二采用仿函数comp比较规则
    	template <class ForwardIterator, class T, class Compare>
    	ForwardIterator upper_bound (ForwardIterator first, ForwardIterator last,
                                   const T& val, Compare comp);
    */
    //版本一
    template <class _ForwardIter, class _Tp>
    inline _ForwardIter upper_bound(_ForwardIter __first, _ForwardIter __last,
                                    const _Tp& __val) {
      __STL_REQUIRES(_ForwardIter, _ForwardIterator);
      __STL_REQUIRES_SAME_TYPE(_Tp,
          typename iterator_traits<_ForwardIter>::value_type);
      __STL_REQUIRES(_Tp, _LessThanComparable);
      return __upper_bound(__first, __last, __val,
                           __DISTANCE_TYPE(__first));
    }
    
    template <class _ForwardIter, class _Tp, class _Compare, class _Distance>
    _ForwardIter __upper_bound(_ForwardIter __first, _ForwardIter __last,
                               const _Tp& __val, _Compare __comp, _Distance*)
    {
      _Distance __len = 0;
      distance(__first, __last, __len);
      _Distance __half;
      _ForwardIter __middle;
    
      while (__len > 0) {
        __half = __len >> 1;
        __middle = __first;
        advance(__middle, __half);
        if (__comp(__val, *__middle))
          __len = __half;
        else {
          __first = __middle;
          ++__first;
          __len = __len - __half - 1;
        }
      }
      return __first;
    }
    //版本二
    template <class _ForwardIter, class _Tp, class _Compare>
    inline _ForwardIter upper_bound(_ForwardIter __first, _ForwardIter __last,
                                    const _Tp& __val, _Compare __comp) {
      __STL_REQUIRES(_ForwardIter, _ForwardIterator);
      __STL_REQUIRES_SAME_TYPE(_Tp,
          typename iterator_traits<_ForwardIter>::value_type);
      __STL_BINARY_FUNCTION_CHECK(_Compare, bool, _Tp, _Tp);
      return __upper_bound(__first, __last, __val, __comp,
                           __DISTANCE_TYPE(__first));
    }
    //函数举例
    /*
    	#include <iostream>     // std::cout
    	#include <algorithm>    // std::lower_bound, std::upper_bound, std::sort
    	#include <vector>       // std::vector
    
    	int main () {
    	  int myints[] = {10,20,30,30,20,10,10,20};
    	  std::vector<int> v(myints,myints+8);           // 10 20 30 30 20 10 10 20
    
    	  std::sort (v.begin(), v.end());                // 10 10 10 20 20 20 30 30
    
    	  std::vector<int>::iterator low,up;
    	  low=std::lower_bound (v.begin(), v.end(), 20); //          ^
    	  up= std::upper_bound (v.begin(), v.end(), 20); //                   ^
    
    	  std::cout << "lower_bound at position " << (low- v.begin()) << '\n';
    	  std::cout << "upper_bound at position " << (up - v.begin()) << '\n';
    
    	  return 0;
    	}
    	Output:
    	lower_bound at position 3
    	upper_bound at position 6
    */
    template <class _ForwardIter, class _Tp, class _Distance>
    pair<_ForwardIter, _ForwardIter>
    __equal_range(_ForwardIter __first, _ForwardIter __last, const _Tp& __val,
                  _Distance*)
    {
      _Distance __len = 0;
      distance(__first, __last, __len);//计算区间的长度len
      _Distance __half;
      _ForwardIter __middle, __left, __right;
    
      while (__len > 0) {//若区间非空
        __half = __len >> 1;//len右移一位，相等于除以2，即half为区间的长度的一半
        __middle = __first;//初始化middle的值
        advance(__middle, __half);//前进middle位置，使其指向区间中间位置
        if (*__middle < __val) {//若指定元素value大于中间元素值，则在右半部分继续查找
    		//下面两行使first指向middle的下一个位置，即右半区间的起始位置
          __first = __middle;
          ++__first;
          __len = __len - __half - 1;//更新待查找区间的长度
        }
        else if (__val < *__middle)//若指定元素value小于中间元素值，则在左半部分继续查找
          __len = __half;//更新待查找区间的长度
        else {//若指定元素value等于中间元素值
    		//在前半部分找lower_bound位置
          __left = lower_bound(__first, __middle, __val);
          advance(__first, __len);
    	  //在后半部分找upper_bound
          __right = upper_bound(++__middle, __first, __val);
          return pair<_ForwardIter, _ForwardIter>(__left, __right);//返回pair对象，第一个迭代器为left，第二个迭代器为right
        }
      }
      return pair<_ForwardIter, _ForwardIter>(__first, __first);
    }
    //查找区间与value相等的相邻重复元素的起始位置和结束位置
    //注意：[first,last)是已排序，思想还是采用二分查找法
    //同样也有两个版本
    /*
    函数功能：Returns the bounds of the subrange that includes all the elements of the range [first,last) with values equivalent to val.
    函数原型：
    default (1)	：版本一默认operator<
    	template <class ForwardIterator, class T>
    		pair<ForwardIterator,ForwardIterator>
        equal_range (ForwardIterator first, ForwardIterator last, const T& val);
    custom (2)	：版本二采用仿函数comp
    	template <class ForwardIterator, class T, class Compare>
    		pair<ForwardIterator,ForwardIterator>
        equal_range (ForwardIterator first, ForwardIterator last, const T& val,
                      Compare comp);
    */
    //版本一
    template <class _ForwardIter, class _Tp>
    inline pair<_ForwardIter, _ForwardIter>
    equal_range(_ForwardIter __first, _ForwardIter __last, const _Tp& __val) {
      __STL_REQUIRES(_ForwardIter, _ForwardIterator);
      __STL_REQUIRES_SAME_TYPE(_Tp, 
           typename iterator_traits<_ForwardIter>::value_type);
      __STL_REQUIRES(_Tp, _LessThanComparable);
      return __equal_range(__first, __last, __val,
                           __DISTANCE_TYPE(__first));
    }
    
    template <class _ForwardIter, class _Tp, class _Compare, class _Distance>
    pair<_ForwardIter, _ForwardIter>
    __equal_range(_ForwardIter __first, _ForwardIter __last, const _Tp& __val,
                  _Compare __comp, _Distance*)
    {
      _Distance __len = 0;
      distance(__first, __last, __len);
      _Distance __half;
      _ForwardIter __middle, __left, __right;
    
      while (__len > 0) {
        __half = __len >> 1;
        __middle = __first;
        advance(__middle, __half);
        if (__comp(*__middle, __val)) {
          __first = __middle;
          ++__first;
          __len = __len - __half - 1;
        }
        else if (__comp(__val, *__middle))
          __len = __half;
        else {
          __left = lower_bound(__first, __middle, __val, __comp);
          advance(__first, __len);
          __right = upper_bound(++__middle, __first, __val, __comp);
          return pair<_ForwardIter, _ForwardIter>(__left, __right);
        }
      }
      return pair<_ForwardIter, _ForwardIter>(__first, __first);
    }           
    //版本二
    template <class _ForwardIter, class _Tp, class _Compare>
    inline pair<_ForwardIter, _ForwardIter>
    equal_range(_ForwardIter __first, _ForwardIter __last, const _Tp& __val,
                _Compare __comp) {
      __STL_REQUIRES(_ForwardIter, _ForwardIterator);
      __STL_REQUIRES_SAME_TYPE(_Tp, 
           typename iterator_traits<_ForwardIter>::value_type);
      __STL_BINARY_FUNCTION_CHECK(_Compare, bool, _Tp, _Tp);
      return __equal_range(__first, __last, __val, __comp,
                           __DISTANCE_TYPE(__first));
    } 
    //equal_range函数举例：
    /*
    	#include <iostream>     // std::cout
    	#include <algorithm>    // std::equal_range, std::sort
    	#include <vector>       // std::vector
    
    	bool mygreater (int i,int j) { return (i>j); }
    
    	int main () {
    	  int myints[] = {10,20,30,30,20,10,10,20};
    	  std::vector<int> v(myints,myints+8);                         // 10 20 30 30 20 10 10 20
    	  std::pair<std::vector<int>::iterator,std::vector<int>::iterator> bounds;
    
    	  // using default comparison:
    	  std::sort (v.begin(), v.end());                              // 10 10 10 20 20 20 30 30
    	  bounds=std::equal_range (v.begin(), v.end(), 20);            //          ^        ^
      
    	  std::cout << "bounds at positions " << (bounds.first - v.begin());
    	  std::cout << " and " << (bounds.second - v.begin()) << '\n';
      
    	  // using "mygreater" as comp:
    	  std::sort (v.begin(), v.end(), mygreater);                   // 30 30 20 20 20 10 10 10
    	  bounds=std::equal_range (v.begin(), v.end(), 20, mygreater); //       ^        ^
    
    	  std::cout << "bounds at positions " << (bounds.first - v.begin());
    	  std::cout << " and " << (bounds.second - v.begin()) << '\n';
    
    	  return 0;
    	}
    	Output：
    	bounds at positions 3 and 6
    	bounds at positions 2 and 5 
    */
    
    //二分查找法
    //注意：[first,last)是已排序
    //同样也有两个版本
    /*
    函数功能：Returns true if any element in the range [first,last) is equivalent to val, and false otherwise.
    函数原型：
    default (1)	：版本一默认operator<
    	template <class ForwardIterator, class T>
    	bool binary_search (ForwardIterator first, ForwardIterator last,
                          const T& val);
    custom (2)	：版本二采用仿函数comp
    	template <class ForwardIterator, class T, class Compare>
    	bool binary_search (ForwardIterator first, ForwardIterator last,
                          const T& val, Compare comp);
    */
    template <class _ForwardIter, class _Tp>
    bool binary_search(_ForwardIter __first, _ForwardIter __last,
                       const _Tp& __val) {
      __STL_REQUIRES(_ForwardIter, _ForwardIterator);
      __STL_REQUIRES_SAME_TYPE(_Tp,
            typename iterator_traits<_ForwardIter>::value_type);
      __STL_REQUIRES(_Tp, _LessThanComparable);
      _ForwardIter __i = lower_bound(__first, __last, __val);//调用二分查找函数，并返回不小于value值的第一个迭代器位置i
      return __i != __last && !(__val < *__i);
    }
    
    
    template <class _ForwardIter, class _Tp, class _Compare>
    bool binary_search(_ForwardIter __first, _ForwardIter __last,
                       const _Tp& __val,
                       _Compare __comp) {
      __STL_REQUIRES(_ForwardIter, _ForwardIterator);
      __STL_REQUIRES_SAME_TYPE(_Tp,
            typename iterator_traits<_ForwardIter>::value_type);
      __STL_BINARY_FUNCTION_CHECK(_Compare, bool, _Tp, _Tp);
      _ForwardIter __i = lower_bound(__first, __last, __val, __comp);//调用二分查找函数，并返回不小于value值的第一个迭代器位置i
      return __i != __last && !__comp(__val, *__i);
    }
    // find_first_of, with and without an explicitly supplied comparison function.
    //以[first2,last2)区间内的某些元素为查找目标，寻找他们在[first1,last1)区间首次出现的位置
    //find_first_of函数有两个版本：
    //版本一：提供默认的equality操作operator==
    //版本二：提供用户自行指定的操作规则comp
    /*
    函数功能：Returns an iterator to the first element in the range [first1,last1) that matches any of the elements in [first2,last2). 
    If no such element is found, the function returns last1.
    函数原型：
    equality (1)：版本一	
    	template <class ForwardIterator1, class ForwardIterator2>
    	ForwardIterator1 find_first_of (ForwardIterator1 first1, ForwardIterator1 last1,
                                       ForwardIterator2 first2, ForwardIterator2 last2);
    predicate (2)：版本二	
    	template <class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
    	ForwardIterator1 find_first_of (ForwardIterator1 first1, ForwardIterator1 last1,
                                       ForwardIterator2 first2, ForwardIterator2 last2,
                                       BinaryPredicate pred);
    */
    //版本一：提供默认的equality操作operator==
    template <class _InputIter, class _ForwardIter>
    _InputIter find_first_of(_InputIter __first1, _InputIter __last1,
                             _ForwardIter __first2, _ForwardIter __last2)
    {
      __STL_REQUIRES(_InputIter, _InputIterator);
      __STL_REQUIRES(_ForwardIter, _ForwardIterator);
      __STL_REQUIRES_BINARY_OP(_OP_EQUAL, bool, 
         typename iterator_traits<_InputIter>::value_type,
         typename iterator_traits<_ForwardIter>::value_type);
    
      for ( ; __first1 != __last1; ++__first1) //若序列一不为空，则遍历序列一，每次指定一个元素
    	  //以下，根据序列二的每个元素
        for (_ForwardIter __iter = __first2; __iter != __last2; ++__iter)
          if (*__first1 == *__iter)//若序列一的元素等于序列二的元素，则表示找到
            return __first1;//返回找到的位置
      return __last1;//否则没找到
    }
    //版本二：提供用户自行指定的操作规则comp
    template <class _InputIter, class _ForwardIter, class _BinaryPredicate>
    _InputIter find_first_of(_InputIter __first1, _InputIter __last1,
                             _ForwardIter __first2, _ForwardIter __last2,
                             _BinaryPredicate __comp)
    {
      __STL_REQUIRES(_InputIter, _InputIterator);
      __STL_REQUIRES(_ForwardIter, _ForwardIterator);
      __STL_BINARY_FUNCTION_CHECK(_BinaryPredicate, bool,
         typename iterator_traits<_InputIter>::value_type,
         typename iterator_traits<_ForwardIter>::value_type);
    
      for ( ; __first1 != __last1; ++__first1) 
        for (_ForwardIter __iter = __first2; __iter != __last2; ++__iter)
          if (__comp(*__first1, *__iter))
            return __first1;
      return __last1;
    }
    //find_first_of函数举例：
    /*
    	#include <iostream>     // std::cout
    	#include <algorithm>    // std::find_first_of
    	#include <vector>       // std::vector
    	#include <cctype>       // std::tolower
    
    	bool comp_case_insensitive (char c1, char c2) {
    	  return (std::tolower(c1)==std::tolower(c2));
    	}
    
    	int main () {
    	  int mychars[] = {'a','b','c','A','B','C'};
    	  std::vector<char> haystack (mychars,mychars+6);
    	  std::vector<char>::iterator it;
    
    	  int needle[] = {'A','B','C'};
    
    	  // using default comparison:
    	  it = find_first_of (haystack.begin(), haystack.end(), needle, needle+3);
    
    	  if (it!=haystack.end())
    		std::cout << "The first match is: " << *it << '\n';
    
    	  // using predicate comparison:
    	  it = find_first_of (haystack.begin(), haystack.end(),
    						  needle, needle+3, comp_case_insensitive);
    
    	  if (it!=haystack.end())
    		std::cout << "The first match is: " << *it << '\n';
    
    	  return 0;
    	}
    	Output:
    	The first match is: A
    	The first match is: a
    */
    
    // find_end, with and without an explicitly supplied comparison function.
    // Search [first2, last2) as a subsequence in [first1, last1), and return
    // the *last* possible match.  Note that find_end for bidirectional iterators
    // is much faster than for forward iterators.
    
    // find_end for forward iterators. 
    //若萃取出来的迭代器类型为正向迭代器forward_iterator_tag，则调用此函数
    template <class _ForwardIter1, class _ForwardIter2>
    _ForwardIter1 __find_end(_ForwardIter1 __first1, _ForwardIter1 __last1,
                             _ForwardIter2 __first2, _ForwardIter2 __last2,
                             forward_iterator_tag, forward_iterator_tag)
    {
      if (__first2 == __last2)//若第二个区间为空
        return __last1;//则直接返回第一个区间的尾端
      else {
        _ForwardIter1 __result = __last1;
        while (1) {
    		//以下利用search函数查找出某个子序列的首次出现点；若找不到直接返回last1
          _ForwardIter1 __new_result
    
            = search(__first1, __last1, __first2, __last2);
          if (__new_result == __last1)//若返回的位置为尾端，则表示没找到
            return __result;//返回last1
          else {//若在[first1,last1)中找到[first2,last2)首次出现的位置，继续准备下一次查找
    		  
            __result = __new_result;//更新返回的位置
            __first1 = __new_result;//更新查找的起始位置
            ++__first1;//确定正确查找起始位置
          }
        }
      }
    }
    //版本二：指定规则
    template <class _ForwardIter1, class _ForwardIter2,
              class _BinaryPredicate>
    _ForwardIter1 __find_end(_ForwardIter1 __first1, _ForwardIter1 __last1,
                             _ForwardIter2 __first2, _ForwardIter2 __last2,
                             forward_iterator_tag, forward_iterator_tag,
                             _BinaryPredicate __comp)
    {
      if (__first2 == __last2)
        return __last1;
      else {
        _ForwardIter1 __result = __last1;
        while (1) {
          _ForwardIter1 __new_result
            = search(__first1, __last1, __first2, __last2, __comp);
          if (__new_result == __last1)
            return __result;
          else {
            __result = __new_result;
            __first1 = __new_result;
            ++__first1;
          }
        }
      }
    }
    
    // find_end for bidirectional iterators.  Requires partial specialization.
    #ifdef __STL_CLASS_PARTIAL_SPECIALIZATION
    //若萃取出来的迭代器类型为双向迭代器bidirectional_iterator_tag，则调用此函数
    template <class _BidirectionalIter1, class _BidirectionalIter2>
    _BidirectionalIter1
    __find_end(_BidirectionalIter1 __first1, _BidirectionalIter1 __last1,
               _BidirectionalIter2 __first2, _BidirectionalIter2 __last2,
               bidirectional_iterator_tag, bidirectional_iterator_tag)
    {
      __STL_REQUIRES(_BidirectionalIter1, _BidirectionalIterator);
      __STL_REQUIRES(_BidirectionalIter2, _BidirectionalIterator);
      //利用反向迭代器很快就可以找到
      typedef reverse_iterator<_BidirectionalIter1> _RevIter1;
      typedef reverse_iterator<_BidirectionalIter2> _RevIter2;
    
      _RevIter1 __rlast1(__first1);
      _RevIter2 __rlast2(__first2);
      //查找时将序列一和序列二逆方向
      _RevIter1 __rresult = search(_RevIter1(__last1), __rlast1,
                                   _RevIter2(__last2), __rlast2);
    
      if (__rresult == __rlast1)//表示没找到
        return __last1;
      else {//找到了
        _BidirectionalIter1 __result = __rresult.base();//转会正常迭代器
        advance(__result, -distance(__first2, __last2));//调整回到子序列的起始位置
        return __result;
      }
    }
    //版本二：指定规则comp
    template <class _BidirectionalIter1, class _BidirectionalIter2,
              class _BinaryPredicate>
    _BidirectionalIter1
    __find_end(_BidirectionalIter1 __first1, _BidirectionalIter1 __last1,
               _BidirectionalIter2 __first2, _BidirectionalIter2 __last2,
               bidirectional_iterator_tag, bidirectional_iterator_tag, 
               _BinaryPredicate __comp)
    {
      __STL_REQUIRES(_BidirectionalIter1, _BidirectionalIterator);
      __STL_REQUIRES(_BidirectionalIter2, _BidirectionalIterator);
      typedef reverse_iterator<_BidirectionalIter1> _RevIter1;
      typedef reverse_iterator<_BidirectionalIter2> _RevIter2;
    
      _RevIter1 __rlast1(__first1);
      _RevIter2 __rlast2(__first2);
      _RevIter1 __rresult = search(_RevIter1(__last1), __rlast1,
                                   _RevIter2(__last2), __rlast2,
                                   __comp);
    
      if (__rresult == __rlast1)
        return __last1;
      else {
        _BidirectionalIter1 __result = __rresult.base();
        advance(__result, -distance(__first2, __last2));
        return __result;
      }
    }
    #endif /* __STL_CLASS_PARTIAL_SPECIALIZATION */
    		  // Dispatching functions for find_end.
    //find_end函数有两个版本：
    //版本一：提供默认的equality操作operator==
    //版本二：提供用户自行指定的操作规则comp
    //注意：这里也有偏特化的知识
    /*函数功能：Searches the range [first1,last1) for the last occurrence of the sequence defined by [first2,last2), 
    and returns an iterator to its first element, or last1 if no occurrences are found.
    函数原型：
    equality (1)：版本一	
    	template <class ForwardIterator1, class ForwardIterator2>
    	ForwardIterator1 find_end (ForwardIterator1 first1, ForwardIterator1 last1,
                                  ForwardIterator2 first2, ForwardIterator2 last2);
    predicate (2)：版本二
    	template <class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
    	ForwardIterator1 find_end (ForwardIterator1 first1, ForwardIterator1 last1,
                                  ForwardIterator2 first2, ForwardIterator2 last2,
                                  BinaryPredicate pred);
    */
    //对外接口的版本一
    template <class _ForwardIter1, class _ForwardIter2>
    inline _ForwardIter1 
    find_end(_ForwardIter1 __first1, _ForwardIter1 __last1, 
             _ForwardIter2 __first2, _ForwardIter2 __last2)
    {
      __STL_REQUIRES(_ForwardIter1, _ForwardIterator);
      __STL_REQUIRES(_ForwardIter2, _ForwardIterator);
      __STL_REQUIRES_BINARY_OP(_OP_EQUAL, bool,
       typename iterator_traits<_ForwardIter1>::value_type,
       typename iterator_traits<_ForwardIter2>::value_type);
      //首先通过iterator_traits萃取出first1和first2的迭代器类型
      //根据不同的迭代器类型调用不同的函数
      return __find_end(__first1, __last1, __first2, __last2,
                        __ITERATOR_CATEGORY(__first1),
                        __ITERATOR_CATEGORY(__first2));
    }
    //对外接口的版本一
    template <class _ForwardIter1, class _ForwardIter2, 
              class _BinaryPredicate>
    inline _ForwardIter1 
    find_end(_ForwardIter1 __first1, _ForwardIter1 __last1, 
             _ForwardIter2 __first2, _ForwardIter2 __last2,
             _BinaryPredicate __comp)
    {
      __STL_REQUIRES(_ForwardIter1, _ForwardIterator);
      __STL_REQUIRES(_ForwardIter2, _ForwardIterator);
      __STL_BINARY_FUNCTION_CHECK(_BinaryPredicate, bool,
       typename iterator_traits<_ForwardIter1>::value_type,
       typename iterator_traits<_ForwardIter2>::value_type);
      //首先通过iterator_traits萃取出first1和first2的迭代器类型
      //根据不同的迭代器类型调用不同的函数
      return __find_end(__first1, __last1, __first2, __last2,
                        __ITERATOR_CATEGORY(__first1),
                        __ITERATOR_CATEGORY(__first2),
                        __comp);
    }
    //find_end函数举例：
    /*
    	#include <iostream>     // std::cout
    	#include <algorithm>    // std::find_end
    	#include <vector>       // std::vector
    
    	bool myfunction (int i, int j) {
    	  return (i==j);
    	}
    
    	int main () {
    	  int myints[] = {1,2,3,4,5,1,2,3,4,5};
    	  std::vector<int> haystack (myints,myints+10);
    
    	  int needle1[] = {1,2,3};
    
    	  // using default comparison:
    	  std::vector<int>::iterator it;
    	  it = std::find_end (haystack.begin(), haystack.end(), needle1, needle1+3);
    
    	  if (it!=haystack.end())
    		std::cout << "needle1 last found at position " << (it-haystack.begin()) << '\n';
    
    	  int needle2[] = {4,5,1};
    
    	  // using predicate comparison:
    	  it = std::find_end (haystack.begin(), haystack.end(), needle2, needle2+3, myfunction);
    
    	  if (it!=haystack.end())
    		std::cout << "needle2 last found at position " << (it-haystack.begin()) << '\n';
    
    	  return 0;
    	}
    	Output:
    	needle1 found at position 5
    	needle2 found at position 3
    */

参考资料：

《STL源码剖析》侯捷

[STL]: http://blog.csdn.net/chenhanzhun/article/details/39698523