https://github.com/ffcactus/leetcode-java
https://github.com/ffcactus/leetcode-java
Last synced: 11 months ago
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- Host: GitHub
- URL: https://github.com/ffcactus/leetcode-java
- Owner: ffcactus
- Created: 2021-06-10T14:04:01.000Z (about 5 years ago)
- Default Branch: master
- Last Pushed: 2022-10-03T11:17:33.000Z (almost 4 years ago)
- Last Synced: 2025-02-21T19:44:53.363Z (over 1 year ago)
- Language: Java
- Size: 49.8 KB
- Stars: 0
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# leetcode-java
# Backtracking
Backtracking is a kind of BFS.
The helper function has the following form.
```java
void backtracking(参数) {
if (终止条件) {
存放结果;
return;
}
for (选择：本层集合中元素（树中节点孩子的数量就是集合的大小）) {
处理节点;
backtracking(路径，选择列表); // 递归
回溯，撤销处理结果
}
}
```
## Typical questions
1. Given 4 numbers, find all the solutions that using them to form a time expression.
For example give your [1,2,3,4], the time expression can be 12:34, 12:43, 13:24, 13:42 and etc.
Here is the feature to this question:
* A solution need includes all the inputs.
* Permutation problem
2. Give your a number string, for example "123345" find out all the possible IPv4 expression.
For example, it can be "12.33.45", "123.3.45", "1.233.4.5" and etc.
Here is the feature to this question:
* A solution must follow the order to the input.