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🧠 LeetCode High-Performance Solutions

LeetCode Solved 🙂

A curated collection of LeetCode problems solved with high-performance, low-complexity algorithms, written in C++ and Python. Each solution is designed to optimize for time complexity, targeting O(1) or O(log n) wherever algorithmically possible.

📈 This repository is more than a solution bank — it's a library of interview-grade, optimized algorithm patterns.


🚀 Features

  • Zero/Logarithmic-Time Complexity First: Most solutions are implemented with an emphasis on reducing time complexity to O(1) / O(log n) where applicable.

  • 🧩 Clean, Readable Code: Code is written in concise style with meaningful variable names and necessary inline explanations.

  • 📂 Organized by Problem ID and Name: All files follow a ID.Problem-Title.cpp or .py naming convention.

  • 📌 Tags and Categories: Problems are categorized by type (e.g. Arrays, Graphs, Dynamic Programming).

  • 🔁 Auto-synced via LeetHub v2.0: All accepted submissions are pushed directly after successful submission.


📎 Example

/solutions/
├── 1.Two-Sum.cpp
├── 20.Valid-Parentheses.py
├── 53.Maximum-Subarray.cpp

🧠 Philosophy

"I do not solve problems to make them go away — I solve them to make them elegant."

For true excellence lies not in mere correctness, but in clarity, grace, and precision. Even though this project has just begun, it is built on a clear philosophy:
Not all accepted answers are equal — only the most refined survive here.


🛠️ Setup (Optional)

This repository is auto-synced via LeetHub v2.0, but can also be manually extended or cloned.


💬 Contribution

Suggestions, optimizations, and alternative approaches are welcome via issues or pull requests.


⭐ Star this repo if:

  • You're preparing for FAANG / big tech interviews
  • You care about algorithm performance and clean code
  • You believe O(1) is better than O(n) 😎

LeetCode Topics

Linked List

0002-add-two-numbers
0019-remove-nth-node-from-end-of-list
0021-merge-two-sorted-lists
0023-merge-k-sorted-lists
0024-swap-nodes-in-pairs
0025-reverse-nodes-in-k-group
0061-rotate-list
0082-remove-duplicates-from-sorted-list-ii
0083-remove-duplicates-from-sorted-list
0086-partition-list
0092-reverse-linked-list-ii
0109-convert-sorted-list-to-binary-search-tree
0114-flatten-binary-tree-to-linked-list
0116-populating-next-right-pointers-in-each-node
0117-populating-next-right-pointers-in-each-node-ii

Math

0002-add-two-numbers
0007-reverse-integer
0009-palindrome-number
0012-integer-to-roman
0013-roman-to-integer
0029-divide-two-integers
0043-multiply-strings
0048-rotate-image
0050-powx-n
0060-permutation-sequence
0062-unique-paths
0066-plus-one
0067-add-binary
0069-sqrtx
0070-climbing-stairs
0089-gray-code
0096-unique-binary-search-trees

Recursion

0002-add-two-numbers
0010-regular-expression-matching
0021-merge-two-sorted-lists
0024-swap-nodes-in-pairs
0025-reverse-nodes-in-k-group
0044-wildcard-matching
0050-powx-n
0060-permutation-sequence

Hash Table

0003-longest-substring-without-repeating-characters
0012-integer-to-roman
0013-roman-to-integer
0017-letter-combinations-of-a-phone-number
0030-substring-with-concatenation-of-all-words
0036-valid-sudoku
0037-sudoku-solver
0041-first-missing-positive
0049-group-anagrams
0073-set-matrix-zeroes
0076-minimum-window-substring
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0106-construct-binary-tree-from-inorder-and-postorder-traversal
0126-word-ladder-ii
0127-word-ladder
0128-longest-consecutive-sequence

String

0003-longest-substring-without-repeating-characters
0005-longest-palindromic-substring
0006-zigzag-conversion
0008-string-to-integer-atoi
0010-regular-expression-matching
0012-integer-to-roman
0013-roman-to-integer
0014-longest-common-prefix
0017-letter-combinations-of-a-phone-number
0020-valid-parentheses
0022-generate-parentheses
0028-find-the-index-of-the-first-occurrence-in-a-string
0030-substring-with-concatenation-of-all-words
0032-longest-valid-parentheses
0038-count-and-say
0043-multiply-strings
0044-wildcard-matching
0049-group-anagrams
0058-length-of-last-word
0065-valid-number
0067-add-binary
0068-text-justification
0071-simplify-path
0072-edit-distance
0076-minimum-window-substring
0079-word-search
0087-scramble-string
0091-decode-ways
0093-restore-ip-addresses
0097-interleaving-string
0115-distinct-subsequences
0125-valid-palindrome
0126-word-ladder-ii
0127-word-ladder
0131-palindrome-partitioning
0392-is-subsequence

Sliding Window

0003-longest-substring-without-repeating-characters
0030-substring-with-concatenation-of-all-words
0076-minimum-window-substring

Array

0004-median-of-two-sorted-arrays
0011-container-with-most-water
0014-longest-common-prefix
0015-3sum
0016-3sum-closest
0018-4sum
0026-remove-duplicates-from-sorted-array
0027-remove-element
0031-next-permutation
0033-search-in-rotated-sorted-array
0034-find-first-and-last-position-of-element-in-sorted-array
0035-search-insert-position
0036-valid-sudoku
0037-sudoku-solver
0039-combination-sum
0040-combination-sum-ii
0041-first-missing-positive
0042-trapping-rain-water
0045-jump-game-ii
0046-permutations
0047-permutations-ii
0048-rotate-image
0049-group-anagrams
0051-n-queens
0053-maximum-subarray
0054-spiral-matrix
0055-jump-game
0056-merge-intervals
0057-insert-interval
0059-spiral-matrix-ii
0063-unique-paths-ii
0064-minimum-path-sum
0066-plus-one
0068-text-justification
0073-set-matrix-zeroes
0074-search-a-2d-matrix
0075-sort-colors
0078-subsets
0079-word-search
0080-remove-duplicates-from-sorted-array-ii
0081-search-in-rotated-sorted-array-ii
0084-largest-rectangle-in-histogram
0085-maximal-rectangle
0088-merge-sorted-array
0090-subsets-ii
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0106-construct-binary-tree-from-inorder-and-postorder-traversal
0108-convert-sorted-array-to-binary-search-tree
0118-pascals-triangle
0119-pascals-triangle-ii
0120-triangle
0121-best-time-to-buy-and-sell-stock
0122-best-time-to-buy-and-sell-stock-ii
0123-best-time-to-buy-and-sell-stock-iii
0128-longest-consecutive-sequence
0130-surrounded-regions

Binary Search

0004-median-of-two-sorted-arrays
0033-search-in-rotated-sorted-array
0034-find-first-and-last-position-of-element-in-sorted-array
0035-search-insert-position
0069-sqrtx
0074-search-a-2d-matrix
0081-search-in-rotated-sorted-array-ii

Divide and Conquer

0004-median-of-two-sorted-arrays
0023-merge-k-sorted-lists
0053-maximum-subarray
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0106-construct-binary-tree-from-inorder-and-postorder-traversal
0108-convert-sorted-array-to-binary-search-tree
0109-convert-sorted-list-to-binary-search-tree

Two Pointers

0005-longest-palindromic-substring
0011-container-with-most-water
0015-3sum
0016-3sum-closest
0018-4sum
0019-remove-nth-node-from-end-of-list
0026-remove-duplicates-from-sorted-array
0027-remove-element
0028-find-the-index-of-the-first-occurrence-in-a-string
0031-next-permutation
0042-trapping-rain-water
0061-rotate-list
0075-sort-colors
0080-remove-duplicates-from-sorted-array-ii
0082-remove-duplicates-from-sorted-list-ii
0086-partition-list
0088-merge-sorted-array
0125-valid-palindrome
0392-is-subsequence

Dynamic Programming

0005-longest-palindromic-substring
0010-regular-expression-matching
0022-generate-parentheses
0032-longest-valid-parentheses
0042-trapping-rain-water
0044-wildcard-matching
0045-jump-game-ii
0053-maximum-subarray
0055-jump-game
0062-unique-paths
0063-unique-paths-ii
0064-minimum-path-sum
0070-climbing-stairs
0072-edit-distance
0085-maximal-rectangle
0087-scramble-string
0091-decode-ways
0095-unique-binary-search-trees-ii
0096-unique-binary-search-trees
0097-interleaving-string
0115-distinct-subsequences
0118-pascals-triangle
0119-pascals-triangle-ii
0120-triangle
0121-best-time-to-buy-and-sell-stock
0122-best-time-to-buy-and-sell-stock-ii
0123-best-time-to-buy-and-sell-stock-iii
0124-binary-tree-maximum-path-sum
0131-palindrome-partitioning
0392-is-subsequence

Greedy

0011-container-with-most-water
0044-wildcard-matching
0045-jump-game-ii
0055-jump-game
0122-best-time-to-buy-and-sell-stock-ii

Trie

0014-longest-common-prefix

Sorting

0015-3sum
0016-3sum-closest
0018-4sum
0047-permutations-ii
0049-group-anagrams
0056-merge-intervals
0075-sort-colors
0088-merge-sorted-array

Backtracking

0017-letter-combinations-of-a-phone-number
0022-generate-parentheses
0037-sudoku-solver
0039-combination-sum
0040-combination-sum-ii
0046-permutations
0047-permutations-ii
0051-n-queens
0052-n-queens-ii
0077-combinations
0078-subsets
0079-word-search
0089-gray-code
0090-subsets-ii
0093-restore-ip-addresses
0095-unique-binary-search-trees-ii
0113-path-sum-ii
0126-word-ladder-ii
0131-palindrome-partitioning

Stack

0020-valid-parentheses
0032-longest-valid-parentheses
0042-trapping-rain-water
0071-simplify-path
0084-largest-rectangle-in-histogram
0085-maximal-rectangle
0094-binary-tree-inorder-traversal
0114-flatten-binary-tree-to-linked-list

Heap (Priority Queue)

0023-merge-k-sorted-lists

Merge Sort

0023-merge-k-sorted-lists

String Matching

0028-find-the-index-of-the-first-occurrence-in-a-string

Bit Manipulation

0029-divide-two-integers
0067-add-binary
0078-subsets
0089-gray-code
0090-subsets-ii

Matrix

0036-valid-sudoku
0037-sudoku-solver
0048-rotate-image
0054-spiral-matrix
0059-spiral-matrix-ii
0063-unique-paths-ii
0064-minimum-path-sum
0073-set-matrix-zeroes
0074-search-a-2d-matrix
0079-word-search
0085-maximal-rectangle
0130-surrounded-regions

Monotonic Stack

0042-trapping-rain-water
0084-largest-rectangle-in-histogram
0085-maximal-rectangle

Simulation

0043-multiply-strings
0054-spiral-matrix
0059-spiral-matrix-ii
0067-add-binary
0068-text-justification

Combinatorics

0062-unique-paths

Memoization

0070-climbing-stairs

Depth-First Search

0079-word-search
0094-binary-tree-inorder-traversal
0098-validate-binary-search-tree
0099-recover-binary-search-tree
0100-same-tree
0101-symmetric-tree
0104-maximum-depth-of-binary-tree
0110-balanced-binary-tree
0111-minimum-depth-of-binary-tree
0112-path-sum
0113-path-sum-ii
0114-flatten-binary-tree-to-linked-list
0116-populating-next-right-pointers-in-each-node
0117-populating-next-right-pointers-in-each-node-ii
0124-binary-tree-maximum-path-sum
0129-sum-root-to-leaf-numbers
0130-surrounded-regions

Tree

0094-binary-tree-inorder-traversal
0095-unique-binary-search-trees-ii
0096-unique-binary-search-trees
0098-validate-binary-search-tree
0099-recover-binary-search-tree
0100-same-tree
0101-symmetric-tree
0102-binary-tree-level-order-traversal
0103-binary-tree-zigzag-level-order-traversal
0104-maximum-depth-of-binary-tree
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0106-construct-binary-tree-from-inorder-and-postorder-traversal
0107-binary-tree-level-order-traversal-ii
0108-convert-sorted-array-to-binary-search-tree
0109-convert-sorted-list-to-binary-search-tree
0110-balanced-binary-tree
0111-minimum-depth-of-binary-tree
0112-path-sum
0113-path-sum-ii
0114-flatten-binary-tree-to-linked-list
0116-populating-next-right-pointers-in-each-node
0117-populating-next-right-pointers-in-each-node-ii
0124-binary-tree-maximum-path-sum
0129-sum-root-to-leaf-numbers

Binary Tree

0094-binary-tree-inorder-traversal
0095-unique-binary-search-trees-ii
0096-unique-binary-search-trees
0098-validate-binary-search-tree
0099-recover-binary-search-tree
0100-same-tree
0101-symmetric-tree
0102-binary-tree-level-order-traversal
0103-binary-tree-zigzag-level-order-traversal
0104-maximum-depth-of-binary-tree
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0106-construct-binary-tree-from-inorder-and-postorder-traversal
0107-binary-tree-level-order-traversal-ii
0108-convert-sorted-array-to-binary-search-tree
0109-convert-sorted-list-to-binary-search-tree
0110-balanced-binary-tree
0111-minimum-depth-of-binary-tree
0112-path-sum
0113-path-sum-ii
0114-flatten-binary-tree-to-linked-list
0116-populating-next-right-pointers-in-each-node
0117-populating-next-right-pointers-in-each-node-ii
0124-binary-tree-maximum-path-sum
0129-sum-root-to-leaf-numbers

Binary Search Tree

0095-unique-binary-search-trees-ii
0096-unique-binary-search-trees
0098-validate-binary-search-tree
0099-recover-binary-search-tree
0108-convert-sorted-array-to-binary-search-tree
0109-convert-sorted-list-to-binary-search-tree

Breadth-First Search

0100-same-tree
0101-symmetric-tree
0102-binary-tree-level-order-traversal
0103-binary-tree-zigzag-level-order-traversal
0104-maximum-depth-of-binary-tree
0107-binary-tree-level-order-traversal-ii
0111-minimum-depth-of-binary-tree
0112-path-sum
0116-populating-next-right-pointers-in-each-node
0117-populating-next-right-pointers-in-each-node-ii
0126-word-ladder-ii
0127-word-ladder
0130-surrounded-regions

Union Find

0128-longest-consecutive-sequence
0130-surrounded-regions

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