c++ string

参考url:
https://blog.csdn.net/tengfei461807914/article/details/52203202
https://blog.csdn.net/qq_23100787/article/details/50475510

这个牛逼
https://www.cnblogs.com/aminxu/p/4686320.html

1. 可以直接比较：

    char s[105] = "asdw"
    string s1 = s;
    string s2("asdm");
    三种比较
    s1==s2
    s1>s2
    s1

2. 重载了+,+=

    string s= "";
    s = s + "a"; //a
    s += "qwe"; //aqwe

3.sort

    string s = "123345123"
    sort(s.begin(), s.end());

4. 初始化

    string s1(5, 'c');   // s1: "ccccc"
    // string s2(5, "ca"); // 出错，这种复制的方式，只能是字符，不能是字符串
    char tmp[100] = {"0123456789"};
    string s2(tmp,5,3);   //tmp可以是char数组，也可以是string类型，5是开始位置，3是拷贝的长度。

5. string做split

    char p1[100] = "1,2,3,4,5,6";
    string sp1 = p1;
    int st=0, end;

    vector<string> strVec;
    while(1){
        end = sp1.find(',',st);
        if(end == string::npos) {
            string now = sp1.substr(st);
            strVec.push_back(now);
            break;
        }

        string now = sp1.substr(st, end-st);
        strVec.push_back(now);
        st = end +1;
    }