2021秋招部分笔试题汇总 第三题

题目：字符串算术运算

描述：定一个字符串式子，返回它的计算结果。算术规则为: k*[encoded_string]，表示其中方括号内部的 encoded_string 正好重复 k 次。注意 k 保证为正整数。e.g. s = "3*[a2*[c]]", 返回 “accaccacc”

输入例子1:

"3*[a2*[c]]"

输出例子1:

"accaccacc"

代码：

import java.util.*;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {
    static StringBuilder sb;

    public String computeString (String str) {
        // write code here
        //2*[b]最少5个字符
        if (str.length() <= 4) {
            return str;
        }

        sb = new StringBuilder(str);

        int right = 0;
        int left = 0;
        while ((right = sb.indexOf("]")) > 0) {
            left = sb.substring(0, right).lastIndexOf('[');
            int t=0;   //记录*前面有几个数字
            int i = left-2;    
            while(i>=0){
                if(sb.charAt(i)>='0'&&sb.charAt(i)<='9'){
                    t++;
                    i--;
                }else{
                    break;
                }
            }
            //处理一个需要转换的字符串
            String res = solution(sb.substring(left - 1-t, right));  //不传入]这两个符号

            sb.replace(left - 1-t, right + 1, res);
        }
        return sb.toString();
    }

    //@parame s为"3*[adnf"类型 ，处理方法
    public static String solution(String s) {
        int left=s.indexOf('[');
        String str=s.substring(left+1,s.length());
        int n=Integer.parseInt(s.substring(0,left-1));
        StringBuilder stringBuilder=new StringBuilder();
        while(n-->0){
            stringBuilder.append(str);
        }
        return stringBuilder.toString();
    }
    public static void main(String[] args) throws IOException {
        BufferedReader bufferedReader=new BufferedReader(new InputStreamReader(System.in));
        String str=bufferedReader.readLine();
        Main main=new Main();
        System.out.println(main.computeString(str));
    }
}