string容器-赋值操作
1.string s1;
s1="hello world!";
2.string s2;
s2=s1;
3.string s3;
s3='a';
4.string s4;
s4.assign("hello world");
5.string s5;
s5.assgin("hello world",5);//前五个拿过来 赋值
6.string s6;
s6.assign(str5);
7.string s7;
s7.assign(10,'a');
###一般用=赋值的多hhh