1. string的函数

#include <bits/stdc++.h>
using namespace std;
int main() {int n,m; cin >> n;string s, a, b, c;cin >> s;for (int i = 0; i < n; i++) {cin >> m;if (m == 1) {cin >> a;s += a;cout << s << endl;}if (m == 2) {int x, y;cin >> x>> y;s = s.substr(x, y);cout << s << endl;}if (m == 3) {int x;cin >> x >> b;s = s.insert(x, b);cout << s << endl;}if (m == 4) {cin  >> c;if (s.find(c,0) < s.size())cout << s.find(c,0) << endl;else cout << -1<<endl;}}return 0;
}