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);
        // 注意 hasNext 和 hasNextLine 的区别
        // while (in.hasNextInt()) { // 注意 while 处理多个 case
            int n = in.nextInt();
            int m = in.nextInt();
            String s = in.next();
            String ss =s;
            for(int i = 0;i<m;i++){  // 修改M次
                s = ss;
                int x = in.nextInt()-1;
                int y = in.nextInt();
                char a = in.next().charAt(0);
                char b = in.next().charAt(0);
                String sb = s.substring(x,y).replace(a,b);
                ss = s.substring(0,x)+sb+s.substring(y,s.length());
            }
            System.out.println(ss);
        // }
    }
}