Algorithms and Data Structures

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Introduction

This repository contains my LeetCode solutions and notes from studying algorithms and data structures. Solutions are grouped by study week, and each problem directory includes its source code and problem description.

Repository Structure

algorithms/
├── docs/           # Guides for organizing and submitting solutions
├── resources/      # Images used by the guides
├── week-1/         # Week 1 solutions
├── week-2-3/       # Week 2 and Week 3 solutions
├── week-4/         # Week 4 solutions
├── week-5/         # Week 5 solutions
├── week-6/         # Week 6 solutions
├── week-7/         # Week 7 solutions
└── README.md       # Repository overview and LeetHub topic index

Practice Progress

Period	Solutions
Week 1	10
Week 2-3	20
Week 4	10
Week 5	10
Week 6	10
Week 7	21
Total	81

Documentation

Guide	Description
Code Organization	Organize solutions in the repository with GitHub Desktop.
LeetHub Submission	Submit accepted LeetCode solutions with LeetHub-3.0.

LeetHub Integration

LeetHub-3.0 uploads accepted solutions and updates the topic index in this README. The weekly grouping is maintained manually and is not managed by the extension.

View the topic index generated by LeetHub-3.0

LeetCode Topics

String

Problem Name	Difficulty
0003-longest-substring-without-repeating-characters	Medium
0020-valid-parentheses	Easy
0049-group-anagrams	Medium
0079-word-search	Medium
0179-largest-number	Medium
0383-ransom-note	Easy
0389-find-the-difference	Easy
0539-minimum-time-difference	Medium
0556-next-greater-element-iii	Medium
0657-robot-return-to-origin	Easy
0796-rotate-string	Easy
0921-minimum-add-to-make-parentheses-valid	Medium
1021-remove-outermost-parentheses	Easy
1209-remove-all-adjacent-duplicates-in-string-ii	Medium
1370-increasing-decreasing-string	Easy
1544-make-the-string-great	Easy
1662-check-if-two-string-arrays-are-equivalent	Easy
1974-minimum-time-to-type-word-using-special-typewriter	Easy

Stack

Problem Name	Difficulty
0020-valid-parentheses	Easy
0150-evaluate-reverse-polish-notation	Medium
0225-implement-stack-using-queues	Easy
0232-implement-queue-using-stacks	Easy
0496-next-greater-element-i	Easy
0735-asteroid-collision	Medium
0739-daily-temperatures	Medium
0921-minimum-add-to-make-parentheses-valid	Medium
1021-remove-outermost-parentheses	Easy
1209-remove-all-adjacent-duplicates-in-string-ii	Medium
1544-make-the-string-great	Easy

Array

Problem Name	Difficulty
0026-remove-duplicates-from-sorted-array	Easy
0034-find-first-and-last-position-of-element-in-sorted-array	Medium
0049-group-anagrams	Medium
0053-maximum-subarray	Medium
0075-sort-colors	Medium
0079-word-search	Medium
0088-merge-sorted-array	Easy
0150-evaluate-reverse-polish-notation	Medium
0153-find-minimum-in-rotated-sorted-array	Medium
0169-majority-element	Easy
0179-largest-number	Medium
0200-number-of-islands	Medium
0209-minimum-size-subarray-sum	Medium
0217-contains-duplicate	Easy
0268-missing-number	Easy
0414-third-maximum-number	Easy
0463-island-perimeter	Easy
0495-teemo-attacking	Easy
0496-next-greater-element-i	Easy
0539-minimum-time-difference	Medium
0542-01-matrix	Medium
0561-array-partition	Easy
0622-design-circular-queue	Medium
0643-maximum-average-subarray-i	Easy
0690-employee-importance	Medium
0704-binary-search	Easy
0733-flood-fill	Easy
0735-asteroid-collision	Medium
0739-daily-temperatures	Medium
0773-sliding-puzzle	Hard
0875-koko-eating-bananas	Medium
0934-shortest-bridge	Medium
0977-squares-of-a-sorted-array	Easy
0994-rotting-oranges	Medium
1304-find-n-unique-integers-sum-up-to-zero	Easy
1346-check-if-n-and-its-double-exist	Easy
1388-pizza-with-3n-slices	Hard
1431-kids-with-the-greatest-number-of-candies	Easy
1662-check-if-two-string-arrays-are-equivalent	Easy
1926-nearest-exit-from-entrance-in-maze	Medium

Two Pointers

Problem Name	Difficulty
0019-remove-nth-node-from-end-of-list	Medium
0026-remove-duplicates-from-sorted-array	Easy
0075-sort-colors	Medium
0086-partition-list	Medium
0088-merge-sorted-array	Easy
0142-linked-list-cycle-ii	Medium
0160-intersection-of-two-linked-lists	Easy
0556-next-greater-element-iii	Medium
0876-middle-of-the-linked-list	Easy
0977-squares-of-a-sorted-array	Easy
1237-find-positive-integer-solution-for-a-given-equation	Medium
1346-check-if-n-and-its-double-exist	Easy

Sorting

Problem Name	Difficulty
0049-group-anagrams	Medium
0075-sort-colors	Medium
0088-merge-sorted-array	Easy
0169-majority-element	Easy
0179-largest-number	Medium
0217-contains-duplicate	Easy
0268-missing-number	Easy
0389-find-the-difference	Easy
0414-third-maximum-number	Easy
0539-minimum-time-difference	Medium
0561-array-partition	Easy
0977-squares-of-a-sorted-array	Easy
1346-check-if-n-and-its-double-exist	Easy

Hash Table

Problem Name	Difficulty
0003-longest-substring-without-repeating-characters	Medium
0049-group-anagrams	Medium
0142-linked-list-cycle-ii	Medium
0160-intersection-of-two-linked-lists	Easy
0169-majority-element	Easy
0217-contains-duplicate	Easy
0268-missing-number	Easy
0383-ransom-note	Easy
0389-find-the-difference	Easy
0496-next-greater-element-i	Easy
0690-employee-importance	Medium
1346-check-if-n-and-its-double-exist	Easy
1370-increasing-decreasing-string	Easy

Counting

Problem Name	Difficulty
0169-majority-element	Easy
0383-ransom-note	Easy
1370-increasing-decreasing-string	Easy

Bit Manipulation

Problem Name	Difficulty
0268-missing-number	Easy
0389-find-the-difference	Easy

Sliding Window

Problem Name	Difficulty
0003-longest-substring-without-repeating-characters	Medium
0209-minimum-size-subarray-sum	Medium
0643-maximum-average-subarray-i	Easy

Simulation

Problem Name	Difficulty
0495-teemo-attacking	Easy
0657-robot-return-to-origin	Easy
0735-asteroid-collision	Medium

Linked List

Problem Name	Difficulty
0019-remove-nth-node-from-end-of-list	Medium
0024-swap-nodes-in-pairs	Medium
0083-remove-duplicates-from-sorted-list	Easy
0086-partition-list	Medium
0109-convert-sorted-list-to-binary-search-tree	Medium
0142-linked-list-cycle-ii	Medium
0160-intersection-of-two-linked-lists	Easy
0203-remove-linked-list-elements	Easy
0206-reverse-linked-list	Easy
0237-delete-node-in-a-linked-list	Medium
0622-design-circular-queue	Medium
0876-middle-of-the-linked-list	Easy

Recursion

Problem Name	Difficulty
0024-swap-nodes-in-pairs	Medium
0203-remove-linked-list-elements	Easy
0206-reverse-linked-list	Easy

Design

Problem Name	Difficulty
0225-implement-stack-using-queues	Easy
0232-implement-queue-using-stacks	Easy
0622-design-circular-queue	Medium

Queue

Problem Name	Difficulty
0225-implement-stack-using-queues	Easy
0232-implement-queue-using-stacks	Easy
0622-design-circular-queue	Medium

Math

Problem Name	Difficulty
0069-sqrtx	Easy
0150-evaluate-reverse-polish-notation	Medium
0268-missing-number	Easy
0367-valid-perfect-square	Easy
0539-minimum-time-difference	Medium
0556-next-greater-element-iii	Medium
1237-find-positive-integer-solution-for-a-given-equation	Medium
1304-find-n-unique-integers-sum-up-to-zero	Easy

Binary Search

Problem Name	Difficulty
0034-find-first-and-last-position-of-element-in-sorted-array	Medium
0069-sqrtx	Easy
0153-find-minimum-in-rotated-sorted-array	Medium
0209-minimum-size-subarray-sum	Medium
0268-missing-number	Easy
0367-valid-perfect-square	Easy
0704-binary-search	Easy
0875-koko-eating-bananas	Medium
1237-find-positive-integer-solution-for-a-given-equation	Medium
1346-check-if-n-and-its-double-exist	Easy

Greedy

Problem Name	Difficulty
0179-largest-number	Medium
0561-array-partition	Easy
0921-minimum-add-to-make-parentheses-valid	Medium
1388-pizza-with-3n-slices	Hard
1974-minimum-time-to-type-word-using-special-typewriter	Easy

Counting Sort

Problem Name	Difficulty
0561-array-partition	Easy

Divide and Conquer

Problem Name	Difficulty
0053-maximum-subarray	Medium
0109-convert-sorted-list-to-binary-search-tree	Medium
0169-majority-element	Easy

Tree

Problem Name	Difficulty
0104-maximum-depth-of-binary-tree	Easy
0109-convert-sorted-list-to-binary-search-tree	Medium
0111-minimum-depth-of-binary-tree	Easy
0226-invert-binary-tree	Easy
0543-diameter-of-binary-tree	Easy
0559-maximum-depth-of-n-ary-tree	Easy
0690-employee-importance	Medium
0872-leaf-similar-trees	Easy

Binary Search Tree

Problem Name	Difficulty
0109-convert-sorted-list-to-binary-search-tree	Medium

Binary Tree

Problem Name	Difficulty
0104-maximum-depth-of-binary-tree	Easy
0109-convert-sorted-list-to-binary-search-tree	Medium
0111-minimum-depth-of-binary-tree	Easy
0226-invert-binary-tree	Easy
0543-diameter-of-binary-tree	Easy
0872-leaf-similar-trees	Easy

Monotonic Stack

Problem Name	Difficulty
0496-next-greater-element-i	Easy
0739-daily-temperatures	Medium

Interactive

Problem Name	Difficulty
1237-find-positive-integer-solution-for-a-given-equation	Medium

Dynamic Programming

Problem Name	Difficulty
0053-maximum-subarray	Medium
0542-01-matrix	Medium
0773-sliding-puzzle	Hard
1388-pizza-with-3n-slices	Hard

Heap (Priority Queue)

Problem Name	Difficulty
1388-pizza-with-3n-slices	Hard

Depth-First Search

Problem Name	Difficulty
0079-word-search	Medium
0104-maximum-depth-of-binary-tree	Easy
0111-minimum-depth-of-binary-tree	Easy
0200-number-of-islands	Medium
0226-invert-binary-tree	Easy
0463-island-perimeter	Easy
0543-diameter-of-binary-tree	Easy
0547-number-of-provinces	Medium
0559-maximum-depth-of-n-ary-tree	Easy
0690-employee-importance	Medium
0733-flood-fill	Easy
0785-is-graph-bipartite	Medium
0841-keys-and-rooms	Medium
0872-leaf-similar-trees	Easy
0934-shortest-bridge	Medium

Breadth-First Search

Problem Name	Difficulty
0104-maximum-depth-of-binary-tree	Easy
0111-minimum-depth-of-binary-tree	Easy
0200-number-of-islands	Medium
0226-invert-binary-tree	Easy
0463-island-perimeter	Easy
0542-01-matrix	Medium
0547-number-of-provinces	Medium
0559-maximum-depth-of-n-ary-tree	Easy
0690-employee-importance	Medium
0733-flood-fill	Easy
0773-sliding-puzzle	Hard
0785-is-graph-bipartite	Medium
0841-keys-and-rooms	Medium
0934-shortest-bridge	Medium
0994-rotting-oranges	Medium
1926-nearest-exit-from-entrance-in-maze	Medium

Matrix

Problem Name	Difficulty
0079-word-search	Medium
0200-number-of-islands	Medium
0463-island-perimeter	Easy
0542-01-matrix	Medium
0733-flood-fill	Easy
0773-sliding-puzzle	Hard
0934-shortest-bridge	Medium
0994-rotting-oranges	Medium
1926-nearest-exit-from-entrance-in-maze	Medium

Union-Find

Problem Name	Difficulty
0200-number-of-islands	Medium
0547-number-of-provinces	Medium
0785-is-graph-bipartite	Medium

Graph Theory

Problem Name	Difficulty
0547-number-of-provinces	Medium
0785-is-graph-bipartite	Medium
0841-keys-and-rooms	Medium

Backtracking

Problem Name	Difficulty
0079-word-search	Medium
0773-sliding-puzzle	Hard

Memoization

Problem Name	Difficulty
0773-sliding-puzzle	Hard

Prefix Sum

Problem Name	Difficulty
0209-minimum-size-subarray-sum	Medium

String Matching

Problem Name	Difficulty
0796-rotate-string	Easy