题解 | 字符串操作

import java.util.Scanner;

// 参考：https://blog.nowcoder.net/n/ce0188a94cab44ca9329c183dd4c9999
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别

        int n = in.nextInt();
        int m = in.nextInt();

        String str = in.next();// 长度为n
        char[] arr = str.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);
            // 开始替换
            for(int j=l-1;j<r;j++){
                if(arr[j] == c1){
                    arr[j] = c2;
                }
            }
        }
        System.out.println(new String(arr));
    }
}