C++进阶STL-常用的遍历算法

小灰灰 2022-05-08 12:06 200阅读 0赞

## for\_each ##

#include "stdafx.h"
    #include <iostream>
    #include <algorithm>
    #include <vector>
    using namespace std;
    
    class Person
    { 
    public:
    	Person(int age, int id) :m_age(age), m_id(id)
    	{ 
    	}
    
    	int m_age;
    	int m_id;
    };
    
    struct Print
    { 
    	void operator()(const Person& p)
    	{ 
    		cout << "age: " << p.m_age << " " << "id: " << p.m_id << endl;
    	}
    };
    int main()
    { 
    
    	vector<Person> v1;
    	Person p1(1, 1), p2(2, 2), p3(3, 3), p4(4, 4), p5(5, 5);
    
    
    	v1.push_back(p4);
    	v1.push_back(p5);
    	v1.push_back(p1);
    	v1.push_back(p2);
    	v1.push_back(p3);
    	v1.push_back(p4);
    	v1.push_back(p4);
    	v1.push_back(p5);
    
    	for_each(v1.begin(), v1.end(), Print());
    
        return 0;
    }

结果：![在这里插入图片描述][20181011164735624]

--------------------

## transform：将一个（或者两个）容器进行操作复制给另一个容器 ##

![在这里插入图片描述][20181011173620200]

#include "stdafx.h"
    #include <iostream>
    #include <algorithm>
    #include <vector>
    #include <functional>
    using namespace std;
    
    class Person
    { 
    public:
    	Person(int age, int id) :m_age(age), m_id(id)
    	{ 
    	}
    	Person()
    	{ 
    
    	}
    	int m_age;
    	int m_id;
    };
    
    struct Print
    { 
    	void operator()(const Person& p)
    	{ 
    		cout << "age: " << p.m_age << " " << "id: " << p.m_id << endl;
    	}
    };
    
    struct op_Increse
    { 
    	Person operator()( Person& p)
    	{ 
    		p.m_age += 1;
    		p.m_id += 1;
    		return p;
    	}
    };
    
    struct op_Increse_2
    { 
    	Person operator()(Person& p1, Person& p2)
    	{ 
    		p1.m_age += p2.m_age;
    		p1.m_id += p2.m_id;
    		return p1;
    	}
    };
    
    int main()
    { 
    
    	vector<Person> v1;
    	Person p1(1, 1), p2(2, 2), p3(3, 3), p4(4, 4), p5(5, 5);
    
    
    	v1.push_back(p4);
    	v1.push_back(p5);
    	v1.push_back(p1);
    	v1.push_back(p2);
    	v1.push_back(p3);
    	v1.push_back(p4);
    	v1.push_back(p4);
    	v1.push_back(p5);
    
    	vector<Person> v2;
    	v2.resize(v1.size());
    	
    	//在第一次调用transform之后，v1每个值也加1，因为op_Increase()函数给的是v1的引用
    	transform(v1.begin(), v1.end(), v2.begin(), op_Increse()); //v1+1=v2,v1作为回调函数的参数，v2作为返回结果
    	for_each(v2.begin(), v2.end(), Print());
    
    	cout << "---------------------------" << endl;
    
    	transform(v1.begin(), v1.end(), v1.begin(), v2.begin(), op_Increse_2());//v2=v1+v2，v1,v2 都作为回调函数的参数，结果再给v2
    	for_each(v2.begin(), v2.end(), Print());
    
        return 0;
    }

结果：  
![在这里插入图片描述][20181011171519257]

[20181011164735624]: /images/20220508/7921bfb57b3c41c388c339e41a8db814.png
[20181011173620200]: /images/20220508/fd7de7a06d514fa29d661f7527883b4c.png
[20181011171519257]: /images/20220508/65f9f988cf9442458da3174c68118777.png