1 string 标准库

#include <iostream>

using std::string;//用到哪个标准库，声明哪个
using std::endl;
using std::cin;
using std::cout;

int main()
{
    //string对象的读写
    string s;
    cin >> s;
    cout << s << endl;
    //获取 字符串 大小
    cout << "the number is :" << s.size() << endl;
    //从string对象获取字符 size_type 字符串类型
    for(string::size_type ix = 0; ix != s.size(); ix++)
    {
        cout << s[ix] << endl;
    }
    //打印第一个元素
    cout << s[0] << endl;
    return 0;
}

ywx@ywx:~/yu/c++_4th/3$ ./3_2
yu
yu
the number is :2
y
u
y