题解 | #牛牛的字符串解码问题#

import java.util.*;


public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param s string字符串
     * @return string字符串
     */
    private  int i = 0;
    public String decodeString (String s) {
        String ans = "";
        // write code here
        for (i = 0; i < s.length();) {
            if (s.charAt(i) >= '0' && s.charAt(i) <= '9') {
                // System.out.println(s.charAt(i));
                ans = ans + dfs(s);
            } else {
                ans = ans + s.charAt(i++);
            }
        }
        return ans;
    }
    public String dfs(String s) {
        String ans = "";
        if (s.charAt(i) >= '0' && s.charAt(i) <= '9') {
            String tem = "";
            int cnt = s.charAt(i) - '0';
            i += 2;
            while (s.charAt(i) != ']' && i < s.length()) {
                if(s.charAt(i) >= '0' && s.charAt(i) <= '9')
                    tem = tem + dfs(s);
                else
                    tem = tem + s.charAt(i++);
            }
            while (cnt > 0) {
                ans = ans + tem;
                cnt--;
            }
        }
        i++;
        return ans;
    }
}