题解 | 字符串操作

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int m = in.nextInt();
        in.nextLine();
        String s = in.nextLine();
        char[] c = s.toCharArray();
        for (int i = 0; i < m; i++) {
            int l = in.nextInt();
            int r = in.nextInt();
            char c1 = in.next().charAt(0);
            char c2 = in.next().charAt(0);
            for (int j = l - 1; j <= r - 1; j++) {
                if (c[j] == c1) {
                    c[j] = c2;
                }
            }
        }
        for (int i = 0; i < c.length; i++) {
            System.out.print(c[i]);
        }
    }
}