C++11的for循环的新用法(推荐)_C/C++

C++11的for循环的新用法(推荐)

2022-02-21 15:25lMonster81 C/C++

C++11这次的更新带来了令很多C++程序员期待已久的for range循环，每次看到javascript， lua里的for range，心想要是C++能有多好，心里别提多酸了。这次C++11不负众望，再也不用羡慕别家人的for range了。下面看下C++11的for循环的新用法

字符串

				?

									string str = "this is a string";

									   for(auto ch : str)

									        cout << ch << endl;

等价于

				?

									for(int i = 0; i < str.size(); i++)

									        cout << str[i] << endl;

									vector

									vector<int> v = {1, 2, 3, 4, 5};

									   for(auto i : v)

									    cout << i << endl;

等价于

				?

									for(int i = 0; i < v.size(); i++)

									    cout << v[i] << endl;

二维vector

				?

									vector<vector<int>> v = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};

									   for(auto i : v)

									    for(auto j : i)

									        cout << j << endl;

等价于

				?

									for(int i = 0; i < v.size(); i++)

									    for(int j = 0; j < v[i].size(); j++)

									        cout << v[i][j] << endl;

数组

				?

									int ary[] = {1, 2, 3, 4, 5};

									   for(auto i : ary)

									        cout << i << endl;

等价于

				?

									for(int i = 0; i < 5; i++)

									        cout << ary[i] << endl;

									map

									map<char, int> m = {{'a', 1}, {'b', 2}, {'c', 3}};

									   for(auto t : m)

									    cout << t.first << ' ' << t.second << endl;

等价于

				?

									for(map<char, int> :: iterator itr = m.begin(); itr != m.end(); itr++)

									    cout << itr ->first << ' ' << itr ->second << endl;