LeetCode Solutions

This repository contains my structured solutions to LeetCode problems. I use this space to strengthen my understanding of Data Structures and Algorithms, improve problem-solving skills, and write optimized, clean implementations.

My focus is on correctness, efficiency, and maintaining clear logic rather than just reaching the final answer.

LeetCode Topics

Array

0001-two-sum
0004-median-of-two-sorted-arrays
0015-3sum
0018-4sum
0026-remove-duplicates-from-sorted-array
0031-next-permutation
0033-search-in-rotated-sorted-array
0034-find-first-and-last-position-of-element-in-sorted-array
0035-search-insert-position
0039-combination-sum
0042-trapping-rain-water
0046-permutations
0048-rotate-image
0053-maximum-subarray
0054-spiral-matrix
0056-merge-intervals
0066-plus-one
0073-set-matrix-zeroes
0075-sort-colors
0080-remove-duplicates-from-sorted-array-ii
0081-search-in-rotated-sorted-array-ii
0088-merge-sorted-array
0118-pascals-triangle
0150-evaluate-reverse-polish-notation
0152-maximum-product-subarray
0153-find-minimum-in-rotated-sorted-array
0162-find-peak-element
0169-majority-element
0189-rotate-array
0198-house-robber
0200-number-of-islands
0229-majority-element-ii
0283-move-zeroes
0287-find-the-duplicate-number
0485-max-consecutive-ones
0493-reverse-pairs
0540-single-element-in-a-sorted-array
0560-subarray-sum-equals-k
0643-maximum-average-subarray-i
0704-binary-search
0961-n-repeated-element-in-size-2n-array
1095-find-in-mountain-array
1351-count-negative-numbers-in-a-sorted-matrix
1365-how-many-numbers-are-smaller-than-the-current-number
1431-kids-with-the-greatest-number-of-candies
1582-special-positions-in-a-binary-matrix
1637-widest-vertical-area-between-two-points-containing-no-points
1679-max-number-of-k-sum-pairs
1769-minimum-number-of-operations-to-move-all-balls-to-each-box
1980-find-unique-binary-string
2011-final-value-of-variable-after-performing-operations
2149-rearrange-array-elements-by-sign
2344-minimum-deletions-to-make-array-divisible
2401-longest-nice-subarray
2789-largest-element-in-an-array-after-merge-operations
2932-maximum-strong-pair-xor-i
2942-find-words-containing-character
3191-minimum-operations-to-make-binary-array-elements-equal-to-one-i
3264-final-array-state-after-k-multiplication-operations-i
3467-transform-array-by-parity
3833-count-dominant-indices
3834-merge-adjacent-equal-elements
3847-find-the-score-difference-in-a-game

Hash Table

0001-two-sum
0003-longest-substring-without-repeating-characters
0013-roman-to-integer
0073-set-matrix-zeroes
0169-majority-element
0202-happy-number
0229-majority-element-ii
0560-subarray-sum-equals-k
0961-n-repeated-element-in-size-2n-array
1365-how-many-numbers-are-smaller-than-the-current-number
1679-max-number-of-k-sum-pairs
1980-find-unique-binary-string
2932-maximum-strong-pair-xor-i
3760-maximum-substrings-with-distinct-start

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
0081-search-in-rotated-sorted-array-ii
0153-find-minimum-in-rotated-sorted-array
0162-find-peak-element
0287-find-the-duplicate-number
0493-reverse-pairs
0540-single-element-in-a-sorted-array
0704-binary-search
1095-find-in-mountain-array
1351-count-negative-numbers-in-a-sorted-matrix
3600-maximize-spanning-tree-stability-with-upgrades

Divide and Conquer

0004-median-of-two-sorted-arrays
0023-merge-k-sorted-lists
0053-maximum-subarray
0169-majority-element
0493-reverse-pairs

Math

0002-add-two-numbers
0009-palindrome-number
0013-roman-to-integer
0048-rotate-image
0066-plus-one
0150-evaluate-reverse-polish-notation
0189-rotate-array
0202-happy-number
0224-basic-calculator
0258-add-digits
0326-power-of-three
1281-subtract-the-product-and-sum-of-digits-of-an-integer
1342-number-of-steps-to-reduce-a-number-to-zero
1523-count-odd-numbers-in-an-interval-range
1688-count-of-matches-in-tournament
1925-count-square-sum-triples
2160-minimum-sum-of-four-digit-number-after-splitting-digits
2235-add-two-integers
2344-minimum-deletions-to-make-array-divisible
2396-strictly-palindromic-number
2520-count-the-digits-that-divide-a-number
3264-final-array-state-after-k-multiplication-operations-i

Matrix

0048-rotate-image
0054-spiral-matrix
0073-set-matrix-zeroes
0200-number-of-islands
1351-count-negative-numbers-in-a-sorted-matrix
1582-special-positions-in-a-binary-matrix

Sorting

0015-3sum
0018-4sum
0056-merge-intervals
0075-sort-colors
0088-merge-sorted-array
0169-majority-element
0229-majority-element-ii
1365-how-many-numbers-are-smaller-than-the-current-number
1637-widest-vertical-area-between-two-points-containing-no-points
1679-max-number-of-k-sum-pairs
2160-minimum-sum-of-four-digit-number-after-splitting-digits
2344-minimum-deletions-to-make-array-divisible
3467-transform-array-by-parity

Counting Sort

0169-majority-element
0229-majority-element-ii
1365-how-many-numbers-are-smaller-than-the-current-number
3467-transform-array-by-parity

String

0003-longest-substring-without-repeating-characters
0013-roman-to-integer
0022-generate-parentheses
0032-longest-valid-parentheses
0125-valid-palindrome
0151-reverse-words-in-a-string
0224-basic-calculator
0344-reverse-string
0392-is-subsequence
0557-reverse-words-in-a-string-iii
0680-valid-palindrome-ii
0709-to-lower-case
1047-remove-all-adjacent-duplicates-in-string
1108-defanging-an-ip-address
1545-find-kth-bit-in-nth-binary-string
1689-partitioning-into-minimum-number-of-deci-binary-numbers
1758-minimum-changes-to-make-alternating-binary-string
1768-merge-strings-alternately
1769-minimum-number-of-operations-to-move-all-balls-to-each-box
1784-check-if-binary-string-has-at-most-one-segment-of-ones
1888-minimum-number-of-flips-to-make-the-binary-string-alternating
1980-find-unique-binary-string
2011-final-value-of-variable-after-performing-operations
2942-find-words-containing-character
3110-score-of-a-string
3760-maximum-substrings-with-distinct-start

Stack

0032-longest-valid-parentheses
0042-trapping-rain-water
0114-flatten-binary-tree-to-linked-list
0150-evaluate-reverse-polish-notation
0224-basic-calculator
0225-implement-stack-using-queues
0232-implement-queue-using-stacks
0234-palindrome-linked-list
1047-remove-all-adjacent-duplicates-in-string
3834-merge-adjacent-equal-elements

Two Pointers

0015-3sum
0018-4sum
0026-remove-duplicates-from-sorted-array
0031-next-permutation
0042-trapping-rain-water
0075-sort-colors
0080-remove-duplicates-from-sorted-array-ii
0088-merge-sorted-array
0125-valid-palindrome
0151-reverse-words-in-a-string
0189-rotate-array
0202-happy-number
0234-palindrome-linked-list
0283-move-zeroes
0287-find-the-duplicate-number
0344-reverse-string
0392-is-subsequence
0557-reverse-words-in-a-string-iii
0680-valid-palindrome-ii
1679-max-number-of-k-sum-pairs
1768-merge-strings-alternately
2149-rearrange-array-elements-by-sign
2396-strictly-palindromic-number

Greedy

0680-valid-palindrome-ii
1689-partitioning-into-minimum-number-of-deci-binary-numbers
2160-minimum-sum-of-four-digit-number-after-splitting-digits
2789-largest-element-in-an-array-after-merge-operations
3600-maximize-spanning-tree-stability-with-upgrades

Enumeration

1925-count-square-sum-triples
3827-count-monobit-integers
3833-count-dominant-indices

Bit Manipulation

0287-find-the-duplicate-number
0693-binary-number-with-alternating-bits
1009-complement-of-base-10-integer
1342-number-of-steps-to-reduce-a-number-to-zero
2401-longest-nice-subarray
2932-maximum-strong-pair-xor-i
3191-minimum-operations-to-make-binary-array-elements-equal-to-one-i
3827-count-monobit-integers

Heap (Priority Queue)

0023-merge-k-sorted-lists
2344-minimum-deletions-to-make-array-divisible
3264-final-array-state-after-k-multiplication-operations-i

Simulation

0054-spiral-matrix
0258-add-digits
1545-find-kth-bit-in-nth-binary-string
1688-count-of-matches-in-tournament
2011-final-value-of-variable-after-performing-operations
2149-rearrange-array-elements-by-sign
3264-final-array-state-after-k-multiplication-operations-i
3834-merge-adjacent-equal-elements
3847-find-the-score-difference-in-a-game

Brainteaser

2396-strictly-palindromic-number

Prefix Sum

0560-subarray-sum-equals-k
1769-minimum-number-of-operations-to-move-all-balls-to-each-box
3129-find-all-possible-stable-binary-arrays-i
3130-find-all-possible-stable-binary-arrays-ii
3191-minimum-operations-to-make-binary-array-elements-equal-to-one-i

Recursion

0002-add-two-numbers
0021-merge-two-sorted-lists
0224-basic-calculator
0234-palindrome-linked-list
0326-power-of-three
1545-find-kth-bit-in-nth-binary-string

Number Theory

0258-add-digits
2344-minimum-deletions-to-make-array-divisible

Trie

2932-maximum-strong-pair-xor-i

Sliding Window

0003-longest-substring-without-repeating-characters
0643-maximum-average-subarray-i
1888-minimum-number-of-flips-to-make-the-binary-string-alternating
2401-longest-nice-subarray
2932-maximum-strong-pair-xor-i
3191-minimum-operations-to-make-binary-array-elements-equal-to-one-i

Dynamic Programming

0022-generate-parentheses
0032-longest-valid-parentheses
0042-trapping-rain-water
0053-maximum-subarray
0118-pascals-triangle
0152-maximum-product-subarray
0198-house-robber
0392-is-subsequence
1888-minimum-number-of-flips-to-make-the-binary-string-alternating
3129-find-all-possible-stable-binary-arrays-i
3130-find-all-possible-stable-binary-arrays-ii

Binary Indexed Tree

0493-reverse-pairs

Segment Tree

0493-reverse-pairs

Merge Sort

0023-merge-k-sorted-lists
0493-reverse-pairs

Ordered Set

0493-reverse-pairs

Linked List

0002-add-two-numbers
0021-merge-two-sorted-lists
0023-merge-k-sorted-lists
0114-flatten-binary-tree-to-linked-list
0234-palindrome-linked-list

Tree

0103-binary-tree-zigzag-level-order-traversal
0114-flatten-binary-tree-to-linked-list
0129-sum-root-to-leaf-numbers
0199-binary-tree-right-side-view
0543-diameter-of-binary-tree

Depth-First Search

0114-flatten-binary-tree-to-linked-list
0129-sum-root-to-leaf-numbers
0199-binary-tree-right-side-view
0200-number-of-islands
0543-diameter-of-binary-tree

Binary Tree

0103-binary-tree-zigzag-level-order-traversal
0114-flatten-binary-tree-to-linked-list
0129-sum-root-to-leaf-numbers
0199-binary-tree-right-side-view
0543-diameter-of-binary-tree

Breadth-First Search

0103-binary-tree-zigzag-level-order-traversal
0199-binary-tree-right-side-view
0200-number-of-islands

Queue

0225-implement-stack-using-queues
0232-implement-queue-using-stacks
3191-minimum-operations-to-make-binary-array-elements-equal-to-one-i

Design

0225-implement-stack-using-queues
0232-implement-queue-using-stacks

Union-Find

0200-number-of-islands
3600-maximize-spanning-tree-stability-with-upgrades

Monotonic Stack

0042-trapping-rain-water

Backtracking

0022-generate-parentheses
0039-combination-sum
0046-permutations
1980-find-unique-binary-string

Interactive

1095-find-in-mountain-array

Database

0197-rising-temperature
0584-find-customer-referee
0595-big-countries
1068-product-sales-analysis-i
1148-article-views-i
1378-replace-employee-id-with-the-unique-identifier
1581-customer-who-visited-but-did-not-make-any-transactions
1683-invalid-tweets

Graph Theory

3600-maximize-spanning-tree-stability-with-upgrades

Minimum Spanning Tree

3600-maximize-spanning-tree-stability-with-upgrades