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
0015-3sum
0018-4sum
0033-search-in-rotated-sorted-array
0034-find-first-and-last-position-of-element-in-sorted-array
0039-combination-sum
0042-trapping-rain-water
0046-permutations
0053-maximum-subarray
0054-spiral-matrix
0055-jump-game
0056-merge-intervals
0073-set-matrix-zeroes
0081-search-in-rotated-sorted-array-ii
0088-merge-sorted-array
0118-pascals-triangle
0128-longest-consecutive-sequence
0137-single-number-ii
0150-evaluate-reverse-polish-notation
0152-maximum-product-subarray
0153-find-minimum-in-rotated-sorted-array
0154-find-minimum-in-rotated-sorted-array-ii
0162-find-peak-element
0167-two-sum-ii-input-array-is-sorted
0189-rotate-array
0204-count-primes
0217-contains-duplicate
0229-majority-element-ii
0238-product-of-array-except-self
0283-move-zeroes
0350-intersection-of-two-arrays-ii
0414-third-maximum-number
0448-find-all-numbers-disappeared-in-an-array
0455-assign-cookies
0485-max-consecutive-ones
0540-single-element-in-a-sorted-array
0560-subarray-sum-equals-k
0566-reshape-the-matrix
0665-non-decreasing-array
0674-longest-continuous-increasing-subsequence
0704-binary-search
0747-largest-number-at-least-twice-of-others
0860-lemonade-change
0977-squares-of-a-sorted-array
1394-find-lucky-integer-in-an-array
1512-number-of-good-pairs
1550-three-consecutive-odds
1578-minimum-time-to-make-rope-colorful
1672-richest-customer-wealth
1752-check-if-array-is-sorted-and-rotated
1822-sign-of-the-product-of-an-array
1838-frequency-of-the-most-frequent-element
2344-minimum-deletions-to-make-array-divisible
2441-largest-positive-integer-that-exists-with-its-negative
2535-difference-between-element-sum-and-digit-sum-of-an-array
2733-neither-minimum-nor-maximum
2784-check-if-array-is-good
2798-number-of-employees-who-met-the-target
2965-find-missing-and-repeated-values
3232-find-if-digit-game-can-be-won
3689-maximum-total-subarray-value-i

Two Pointers

0015-3sum
0018-4sum
0028-find-the-index-of-the-first-occurrence-in-a-string
0042-trapping-rain-water
0061-rotate-list
0088-merge-sorted-array
0125-valid-palindrome
0167-two-sum-ii-input-array-is-sorted
0189-rotate-array
0202-happy-number
0234-palindrome-linked-list
0283-move-zeroes
0344-reverse-string
0345-reverse-vowels-of-a-string
0350-intersection-of-two-arrays-ii
0392-is-subsequence
0455-assign-cookies
0977-squares-of-a-sorted-array
2441-largest-positive-integer-that-exists-with-its-negative
3884-first-matching-character-from-both-ends

Hash Table

0001-two-sum
0003-longest-substring-without-repeating-characters
0017-letter-combinations-of-a-phone-number
0073-set-matrix-zeroes
0128-longest-consecutive-sequence
0202-happy-number
0217-contains-duplicate
0229-majority-element-ii
0242-valid-anagram
0350-intersection-of-two-arrays-ii
0387-first-unique-character-in-a-string
0448-find-all-numbers-disappeared-in-an-array
0560-subarray-sum-equals-k
1394-find-lucky-integer-in-an-array
1512-number-of-good-pairs
2441-largest-positive-integer-that-exists-with-its-negative
2784-check-if-array-is-good
2965-find-missing-and-repeated-values

Math

0007-reverse-integer
0009-palindrome-number
0070-climbing-stairs
0150-evaluate-reverse-polish-notation
0189-rotate-array
0202-happy-number
0204-count-primes
0224-basic-calculator
0326-power-of-three
0509-fibonacci-number
1281-subtract-the-product-and-sum-of-digits-of-an-integer
1486-xor-operation-in-an-array
1512-number-of-good-pairs
1822-sign-of-the-product-of-an-array
2344-minimum-deletions-to-make-array-divisible
2520-count-the-digits-that-divide-a-number
2535-difference-between-element-sum-and-digit-sum-of-an-array
2652-sum-multiples
2965-find-missing-and-repeated-values
3232-find-if-digit-game-can-be-won

Counting

0229-majority-element-ii
0387-first-unique-character-in-a-string
1394-find-lucky-integer-in-an-array
1512-number-of-good-pairs

String

0003-longest-substring-without-repeating-characters
0017-letter-combinations-of-a-phone-number
0028-find-the-index-of-the-first-occurrence-in-a-string
0032-longest-valid-parentheses
0125-valid-palindrome
0224-basic-calculator
0242-valid-anagram
0344-reverse-string
0345-reverse-vowels-of-a-string
0387-first-unique-character-in-a-string
0392-is-subsequence
0657-robot-return-to-origin
1578-minimum-time-to-make-rope-colorful
3884-first-matching-character-from-both-ends

Dynamic Programming

0032-longest-valid-parentheses
0042-trapping-rain-water
0053-maximum-subarray
0055-jump-game
0070-climbing-stairs
0118-pascals-triangle
0152-maximum-product-subarray
0392-is-subsequence
0509-fibonacci-number
1578-minimum-time-to-make-rope-colorful

Greedy

0055-jump-game
0455-assign-cookies
0860-lemonade-change
1578-minimum-time-to-make-rope-colorful
1838-frequency-of-the-most-frequent-element
3689-maximum-total-subarray-value-i

Divide and Conquer

0053-maximum-subarray
0190-reverse-bits
0191-number-of-1-bits

Bit Manipulation

0137-single-number-ii
0190-reverse-bits
0191-number-of-1-bits
1486-xor-operation-in-an-array

Recursion

0021-merge-two-sorted-lists
0025-reverse-nodes-in-k-group
0224-basic-calculator
0234-palindrome-linked-list
0326-power-of-three
0509-fibonacci-number

Sorting

0015-3sum
0018-4sum
0056-merge-intervals
0088-merge-sorted-array
0217-contains-duplicate
0229-majority-element-ii
0242-valid-anagram
0350-intersection-of-two-arrays-ii
0414-third-maximum-number
0455-assign-cookies
0747-largest-number-at-least-twice-of-others
0977-squares-of-a-sorted-array
1838-frequency-of-the-most-frequent-element
2344-minimum-deletions-to-make-array-divisible
2441-largest-positive-integer-that-exists-with-its-negative
2733-neither-minimum-nor-maximum
2784-check-if-array-is-good

Matrix

0054-spiral-matrix
0073-set-matrix-zeroes
0566-reshape-the-matrix
1672-richest-customer-wealth
2965-find-missing-and-repeated-values

Memoization

0070-climbing-stairs
0509-fibonacci-number

Tree

0098-validate-binary-search-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

0098-validate-binary-search-tree
0114-flatten-binary-tree-to-linked-list
0129-sum-root-to-leaf-numbers
0199-binary-tree-right-side-view
0543-diameter-of-binary-tree

Binary Tree

0098-validate-binary-search-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

Linked List

0021-merge-two-sorted-lists
0025-reverse-nodes-in-k-group
0061-rotate-list
0114-flatten-binary-tree-to-linked-list
0234-palindrome-linked-list
0328-odd-even-linked-list

Stack

0032-longest-valid-parentheses
0042-trapping-rain-water
0114-flatten-binary-tree-to-linked-list
0150-evaluate-reverse-polish-notation
0224-basic-calculator
0234-palindrome-linked-list

Binary Search Tree

0033-search-in-rotated-sorted-array
0034-find-first-and-last-position-of-element-in-sorted-array
0081-search-in-rotated-sorted-array-ii
0098-validate-binary-search-tree
0153-find-minimum-in-rotated-sorted-array
0154-find-minimum-in-rotated-sorted-array-ii
0162-find-peak-element
0167-two-sum-ii-input-array-is-sorted
0350-intersection-of-two-arrays-ii
0540-single-element-in-a-sorted-array
0704-binary-search
1838-frequency-of-the-most-frequent-element

Simulation

0054-spiral-matrix
0566-reshape-the-matrix
0657-robot-return-to-origin

Backtracking

0017-letter-combinations-of-a-phone-number
0039-combination-sum
0046-permutations

Enumeration

0204-count-primes

Number Theory

0204-count-primes
2344-minimum-deletions-to-make-array-divisible

Union-Find

0128-longest-consecutive-sequence

Monotonic Stack

0042-trapping-rain-water

Heap (Priority Queue)

2344-minimum-deletions-to-make-array-divisible

Prefix Sum

0238-product-of-array-except-self
0560-subarray-sum-equals-k
1838-frequency-of-the-most-frequent-element

Sliding Window

0003-longest-substring-without-repeating-characters
1838-frequency-of-the-most-frequent-element

Database

0197-rising-temperature
0570-managers-with-at-least-5-direct-reports
0577-employee-bonus
0584-find-customer-referee
0595-big-countries
0620-not-boring-movies
1068-product-sales-analysis-i
1148-article-views-i
1251-average-selling-price
1280-students-and-examinations
1378-replace-employee-id-with-the-unique-identifier
1581-customer-who-visited-but-did-not-make-any-transactions
1661-average-time-of-process-per-machine
1683-invalid-tweets
1757-recyclable-and-low-fat-products
1934-confirmation-rate

String Matching

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

Queue

0387-first-unique-character-in-a-string