> For the complete documentation index, see [llms.txt](https://mnunknown.gitbook.io/algorithm-notes/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mnunknown.gitbook.io/algorithm-notes/stringff0c_zi_fu_chuan_lei/g_decode_string.md).

# (G) Decode String

## [Decode String](https://leetcode.com/problems/decode-string/)

匆忙写的，有点丑。。之后要优化下。

步骤上不麻烦，遇到嵌套的括号，就把原始 String 变成更小的子问题，递归处理就好了。于是这题操作上总共就三件事：

* 一边扫一边记录当前数字，times 初始化 = 0；
* 找到当前括号的匹配括号；
* 括号之间就是一个新的子问题，递归处理之后把结果用循环添加就好了。

  ```java
  public String decodeString(String s) {
      if(s == null || s.length() == 0) return "";
      StringBuilder sb = new StringBuilder();

      for(int i = 0; i < s.length(); i++){
          char chr = s.charAt(i);
          if(Character.isDigit(chr)){
              int times = 0;
              while(i < s.length() && s.charAt(i) != '['){
                  times = times * 10 + (s.charAt(i) - '0');
                  i ++;
              }
              int matchIndex = findMatchIndex(s, i);
              String repeat = decodeString(s.substring(i + 1, matchIndex));

              for(int time = 0; time < times; time++){
                  sb.append(repeat);
              }
              i = matchIndex;
          } else {
              sb.append(chr);
          }
      }
      return sb.toString();
  }

  private int findMatchIndex(String s, int index){
      int count = 0;
      for(; index < s.length(); index++){
          if(s.charAt(index) == '[') count ++;
          else if(s.charAt(index) == ']') count --;

          if(count == 0) break;
      }

      return index;
  }
  ```


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://mnunknown.gitbook.io/algorithm-notes/stringff0c_zi_fu_chuan_lei/g_decode_string.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.