题解 | 字符串操作

#include <iostream>
#include <string>
using namespace std;

int main() {
    int n, m;
    cin >> n >> m;

    string s;
    cin >> s;

    while (m--) {
        int left, right;
        cin >> left >> right;
        // cout << left << right << endl;
        char c1, c2;
        cin >> c1 >> c2;
        // cout << c1 << c2 << endl;

        for (int i = left; i <= right; ++i) {
            if (s[i - 1] == c1) {
                s[i - 1] = c2;
            }
        }
    }

    cout << s;
    return 0;
}