# leetcode

**Repository Path**: elord/leetcode

## Basic Information

- **Project Name**: leetcode
- **Description**: leetcode同步代码
- **Primary Language**: Unknown
- **License**: MIT
- **Default Branch**: main
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2026-01-28
- **Last Updated**: 2026-11-04

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# LeetCode Java Solutions

This is a repository of LeetCode algorithm solutions implemented in Java. The solutions are organized by difficulty level (Easy, Medium, Hard), and include detailed problem-solving approaches and test cases.

## Project Features

- **Clear Structure**: Solutions are categorized into three difficulty levels, each with its own solution class.
- **Comprehensive Testing**: Full unit tests provided, covering major functionalities.
- **Tool Support**: Includes commonly used data structure utility classes (e.g., ListNode for linked lists).
- **Detailed Comments**: Core methods are thoroughly documented with Chinese comments.

## Project Structure

```
src/main/java/org/example/
├── ListNode.java          # Linked list node utility class
├── Utils.java             # General utility methods
├── hard/
│   └── OtherSolution.java  # Hard-level other algorithms
└── mid/
    ├── HardSolution.java   # Hard-level algorithms (under Medium category)
    ├── MidSolution.java    # Medium-difficulty algorithms
    └── SimpleSolution.java # Easy-difficulty algorithms
```

## Main Features

### Easy Solutions (SimpleSolution)
- Calculate length of the last word
- Add one to an array
- Add binary strings
- Compute square root
- Remove duplicates from a linked list

### Medium Solutions (MidSolution)
- Combination Sum series problems
- String multiplication
- Permutations and permutation with duplicates
- Matrix rotation
- Group anagrams
- Spiral matrix traversal
- Jump game
- Merge intervals
- Matrix generation
- Rotate linked list
- Path counting
- Simplify path
- Edit distance
- Set matrix zeros
- Search in 2D matrix
- Sort colors
- Combination problems
- Generate subsets
- Word search

### Hard Solutions (HardSolution/OtherSolution)
- First missing positive number
- Trapping rain water
- N-Queens problem
- Permutation sequence
- Number validation
- Text justification
- Minimum window substring
- Maximum rectangle area

## Dependency Configuration

The project uses Maven for building and management. Required environment:

- JDK 8 or higher
- Maven 3.x

Main dependencies:
- JUnit 4.13.2 (testing framework)

## Quick Start

1. Clone the project:
```bash
git clone https://gitee.com/elord/leetcode.git
```

2. Compile with Maven:
```bash
mvn clean compile
```

3. Run tests:
```bash
mvn test
```

## Sample Code

**Remove duplicates from a linked list:**
```java
ListNode head = new ListNode(1, new ListNode(1, new ListNode(2)));
ListNode result = new SimpleSolution().deleteDuplicates(head);
// Output: 1 -> 2
```

**Calculate combination sum:**
```java
int[] candidates = {2, 3, 6, 7};
List<List<Integer>> result = new MidSolution().combinationSum(candidates, 7);
// Returns all combinations that sum to 7
```

## Test Coverage

The project includes comprehensive unit tests written using the JUnit framework:

- `HardSolutionTest` - Tests for hard-level algorithms
- `MidSolutionTest` - Tests for medium-level algorithms
- `SimpleSolutionTest` - Tests for easy-level algorithms

Run tests:
```bash
mvn test -Dtest=*Test
```

## Utility Classes

### ListNode
Linked list node class for handling linked list problems:
```java
ListNode node = new ListNode(1);
ListNode nodeWithNext = new ListNode(1, nextNode);
```

### Utils
Provides common helper methods:
- `generateListNodes(int... vals)` - Generate a linked list from input values
- `printTwoDimensionArray(int[][] arr)` - Print a 2D array

## License

This project is intended solely for learning and communication purposes.

## Contribution Guidelines

Pull requests and issues are welcome to improve code quality. When submitting code, please ensure:
- Follow existing code style
- Add necessary comments
- Provide corresponding test cases