What is leetcode?

This repository is a personal collection of Java solutions to LeetCode coding problems, organized by the type of algorithm or data structure each problem uses. LeetCode is a popular platform where programmers practice solving algorithmic puzzles, commonly used to prepare for technical job interviews at software companies. The problems are grouped into categories rather than by problem number. Categories include hash tables, linked list operations, two-pointer and sliding window techniques, string manipulation, number operations, arrays, stacks, heaps, recursion, divide and conquer, dynamic programming, backtracking, prefix trees, and various tree traversal methods. Each category contains links to the specific problem folders in the repository, where you can find the Java code. The repository also includes a separate section collecting interview preparation notes, linked from a file called Rocket.md. The README is written in Chinese, and an English version is available at a separate link. This is a study and reference resource aimed at programmers preparing for technical interviews. It is not a library or tool you install into a project. If you want to browse solutions organized by technique rather than problem number, or see how a particular algorithmic pattern applies across multiple problems, this repository provides that structure.