substr

#include<cstdio>#include<cstdlib>#include<cstring>#include<string>#include<iostream>#include<algorithm>using namespace std;int main(){    string s("0123456789");    string s1=s.substr(0);//只有一个数字0表示从下标为0开始一直到结尾：sub1 = "0123456789"    string s2=s.substr(5,3);//从下标为5开始截取长度为3位：sub2 = "567"    cout<<s1<<endl<<s2<<endl;    return 0;}