C++11的for循环使用auto的新用法

不念不忘少年蓝@ 2022-11-06 07:59 437阅读 0赞

## C++11的for循环使用auto的新用法 ##

for(auto a:vec)  
\{  
cout<<a<<" ";  
\}

#include<bits/stdc++.h>
    using namespace std;
    int main()
    {
        
    	vector<int> vec;
    	for(int i=0; i<10; i++)
    	{
        
    		vec.push_back(i);
    	}
    
    
    	for(auto a:vec)
    	{
        
    		cout<<a<<" ";
    	}
        cout << endl;
    
        vector<int>::iterator it = vec.begin();
        for (it; it != vec.end();it++)
        {
        
            cout << *it << " ";
        }
            system("pause");
        return 0;
     }

![在这里插入图片描述][2021030820234386.png]

void printLN(T value)  
\{  
cout << value <<" ";  
\}  
for\_each(vec.begin(), vec.end(), printLN);  
for\_each(iterator,iterator,callback);

前两个参数列表是遍历容器的迭代器，第三个参数是对应的回调函数

回调函数的原理都是将参数传递至相应的函数体，再进行操作

#include<bits/stdc++.h>
    using namespace std;
    template<typename T>
    void printLN(T value)
    {
        
        cout << value <<" ";
    }
    int main()
    {
        
    	vector<int> vec;
    	for(int i=0; i<10; i++)
    	{
        
    		vec.push_back(i);
    	}
        for_each(vec.begin(), vec.end(), printLN<int>);
    
            system("pause");
        return 0;
     }

![在这里插入图片描述][20210308203032991.png]

#include<bits/stdc++.h>
    using namespace std;
    
    int main()
    {
        
        //array
        int array[] = {
        1, 2, 3, 4, 5};
        for(auto a:array)
        {
        
            cout << a << " ";
        }
        cout << endl;
    
    
        //string
        string str = "hello world!";
        for(auto b:str)
        {
        
            cout << b << " ";
        }
        cout << endl;
    
    
        //vector
        vector<int> vec = {
        1, 3, 5, 7};
        for(auto c:vec)
        {
        
            cout << c << " ";
        }
        cout << endl;
    
    
        //map
        map<int, string> mymap = {
        {
        1, "abc"}, {
        2, "bca"}, {
        3, "acb"}};
        for(auto d:mymap)
        {
        
            cout << d.first << " " << d.second << " ";
        }
        cout << endl;
    
        cout << "另一种方式：";
    
        for (map<int, string>::iterator it = mymap.begin(); it != mymap.end(); it++)
        {
        
            cout<< it->first<<" "<<it->second<< " ";
        }
        cout << endl;
        system("pause");
    
        return 0;
     }

![在这里插入图片描述][20210308205659629.png]

[2021030820234386.png]: /images/20221023/9a42449c4e56428bbcff46dc6c9312b3.png
[20210308203032991.png]: /images/20221023/b9a83363c0dc48ffb5ef4f416d16e4e4.png
[20210308205659629.png]: /images/20221023/470aa85695124e97b4af53bda6c85f4f.png