【String】常用库函数系列一（替换(replace)，删除(erase)，取子串(substr) )

朱雀 2022-05-14 02:12 156阅读 0赞

导航

*   *   *  String:: replace
         *  String::erase
         *  String::substr

### String:: replace ###

string (1)  
    string& replace (size_t pos,  size_t len,  const string& str);
    string& replace (iterator i1, iterator i2, const string& str);
    substring (2)   
    string& replace (size_t pos,  size_t len,  const string& str,
                     size_t subpos, size_t sublen);
    c-string (3)    
    string& replace (size_t pos,  size_t len,  const char* s);
    string& replace (iterator i1, iterator i2, const char* s);
    buffer (4)  
    string& replace (size_t pos,  size_t len,  const char* s, size_t n);
    string& replace (iterator i1, iterator i2, const char* s, size_t n);
    fill (5)    
    string& replace (size_t pos,  size_t len,  size_t n, char c);
    string& replace (iterator i1, iterator i2, size_t n, char c);
    range (6)   
    template <class InputIterator>
      string& replace (iterator i1, iterator i2,
                       InputIterator first, InputIterator last);

参数介绍：  
str : 用来替换的字符串  
pos：原字符串替换的第一个字符的位置  
len： 替换子串的长度  
subpos: 用来替换的字符串的起始位置  
sublen:用来替换的字符串的长度  
s: char类型数组的首地址  
n: 替换字符的数量  
c: 用来替换的字符  
first: 原字符串替换的初始位置  
last:原字符串替换的末位置 （重点提示，\[first,last) 这是左闭右开的）

如果对上面的参数还比较模糊，可以参考下面代码：

举例：

// replacing in a string
    #include <iostream>
    #include <string>
    
    int main ()
    {
      std::string base="this is a test string.";
      std::string str2="n example";
      std::string str3="sample phrase";
      std::string str4="useful.";
    
      // replace signatures used in the same order as described above:
    
      // Using positions:                 0123456789*123456789*12345
      std::string str=base;           // "this is a test string."
      str.replace(9,5,str2);          // "this is an example string." (1)
      str.replace(19,6,str3,7,6);     // "this is an example phrase." (2)
      str.replace(8,10,"just a");     // "this is just a phrase."     (3)
      str.replace(8,6,"a shorty",7);  // "this is a short phrase."    (4)
      str.replace(22,1,3,'!');        // "this is a short phrase!!!"  (5)
    
      // Using iterators:                                               0123456789*123456789*
      str.replace(str.begin(),str.end()-3,str3);                    // "sample phrase!!!"      (1)
      str.replace(str.begin(),str.begin()+6,"replace");             // "replace phrase!!!"     (3)
      str.replace(str.begin()+8,str.begin()+14,"is coolness",7);    // "replace is cool!!!"    (4)
      str.replace(str.begin()+12,str.end()-4,4,'o');                // "replace is cooool!!!"  (5)
      str.replace(str.begin()+11,str.end(),str4.begin(),str4.end());// "replace is useful."    (6)
      std::cout << str << '\n';
      return 0;
    }

### String::erase ###

sequence (1)    
    string& erase (size_t pos = 0, size_t len = npos);
    character (2)   
    iterator erase (iterator p);
    range (3)   
    iterator erase (iterator first, iterator last);

参数说明：  
pos:待删除的第一个字符的位置  
len:待删除字串的长度  
p:待删除字符的迭代器指向的位置  
first,last:待删除子串的迭代器起始和结束位置 （也是左闭右开）

举例：

// string::erase
    #include <iostream>
    #include <string>
    
    int main ()
    {
      std::string str ("This is an example sentence.");
      std::cout << str << '\n';
                                               // "This is an example sentence."
      str.erase (10,8);                        //            ^^^^^^^^
      std::cout << str << '\n';
                                               // "This is an sentence."
      str.erase (str.begin()+9);               //           ^
      std::cout << str << '\n';
                                               // "This is a sentence."
      str.erase (str.begin()+5, str.end()-9);  //       ^^^^^
      std::cout << str << '\n';
                                               // "This sentence."
      return 0;
    }
    
    【OUTPUT】
    This is an example sentence.
    This is an sentence.
    This is a sentence.
    This sentence.

### String::substr ###

string substr (size_t pos = 0, size_t len = npos) const;

参数说明：

Pos ：要复制的子串的第一个字符的位置，不能超过原字符串长度  
Len：要复制的子串的长度，如果不写，则从Pos位置一直到原字符串的结尾处

举例：

// string::substr
    #include <iostream>
    #include <string>
    
    int main ()
    {
      std::string str="We think in generalities, but we live in details.";
                                               // (quoting Alfred N. Whitehead)
    
      std::string str2 = str.substr (3,5);     // "think"
    
      std::size_t pos = str.find("live");      // position of "live" in str
    
      std::string str3 = str.substr (pos);     // get from "live" to the end
    
      std::cout << str2 << '\n' << str3 << '\n';
    
      return 0;
    }
    
    【OUTPUT】
    think
    live in details.