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
0014-longest-common-prefix
0015-3sum
0016-3sum-closest
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
0036-valid-sudoku
0039-combination-sum
0042-trapping-rain-water
0046-permutations
0048-rotate-image
0049-group-anagrams
0053-maximum-subarray
0054-spiral-matrix
0056-merge-intervals
0063-unique-paths-ii
0064-minimum-path-sum
0066-plus-one
0073-set-matrix-zeroes
0074-search-a-2d-matrix
0075-sort-colors
0080-remove-duplicates-from-sorted-array-ii
0081-search-in-rotated-sorted-array-ii
0088-merge-sorted-array
0118-pascals-triangle
0120-triangle
0121-best-time-to-buy-and-sell-stock
0130-surrounded-regions
0150-evaluate-reverse-polish-notation
0152-maximum-product-subarray
0153-find-minimum-in-rotated-sorted-array
0162-find-peak-element
0167-two-sum-ii-input-array-is-sorted
0169-majority-element
0189-rotate-array
0198-house-robber
0200-number-of-islands
0213-house-robber-ii
0217-contains-duplicate
0229-majority-element-ii
0238-product-of-array-except-self
0239-sliding-window-maximum
0283-move-zeroes
0287-find-the-duplicate-number
0334-increasing-triplet-subsequence
0347-top-k-frequent-elements
0410-split-array-largest-sum
0416-partition-equal-subset-sum
0455-assign-cookies
0485-max-consecutive-ones
0493-reverse-pairs
0540-single-element-in-a-sorted-array
0542-01-matrix
0560-subarray-sum-equals-k
0643-maximum-average-subarray-i
0645-set-mismatch
0704-binary-search
0733-flood-fill
0739-daily-temperatures
0746-min-cost-climbing-stairs
0835-image-overlap
0853-car-fleet
0860-lemonade-change
0875-koko-eating-bananas
0931-minimum-falling-path-sum
0961-n-repeated-element-in-size-2n-array
0994-rotting-oranges
1004-max-consecutive-ones-iii
1011-capacity-to-ship-packages-within-d-days
1020-number-of-enclaves
1095-find-in-mountain-array
1283-find-the-smallest-divisor-given-a-threshold
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
1463-cherry-pickup-ii
1470-shuffle-the-array
1477-find-two-non-overlapping-sub-arrays-each-with-target-sum
1482-minimum-number-of-days-to-make-m-bouquets
1539-kth-missing-positive-number
1582-special-positions-in-a-binary-matrix
1637-widest-vertical-area-between-two-points-containing-no-points
1658-minimum-operations-to-reduce-x-to-zero
1679-max-number-of-k-sum-pairs
1732-find-the-highest-altitude
1769-minimum-number-of-operations-to-move-all-balls-to-each-box
1807-evaluate-the-bracket-pairs-of-a-string
1838-frequency-of-the-most-frequent-element
1929-concatenation-of-array
1967-number-of-strings-that-appear-as-substrings-in-word
1980-find-unique-binary-string
2011-final-value-of-variable-after-performing-operations
2094-finding-3-digit-even-numbers
2149-rearrange-array-elements-by-sign
2267-check-if-there-is-a-valid-parentheses-string-path
2333-minimum-sum-of-squared-difference
2344-minimum-deletions-to-make-array-divisible
2367-number-of-arithmetic-triplets
2401-longest-nice-subarray
2441-largest-positive-integer-that-exists-with-its-negative
2553-separate-the-digits-in-an-array
2574-left-and-right-sum-differences
2789-largest-element-in-an-array-after-merge-operations
2932-maximum-strong-pair-xor-i
2942-find-words-containing-character
2958-length-of-longest-subarray-with-at-most-k-frequency
2996-smallest-missing-integer-greater-than-sequential-prefix-sum
3191-minimum-operations-to-make-binary-array-elements-equal-to-one-i
3264-final-array-state-after-k-multiplication-operations-i
3414-maximum-score-of-non-overlapping-intervals
3467-transform-array-by-parity
3471-find-the-largest-almost-missing-integer
3483-unique-3-digit-even-numbers
3524-find-x-value-of-array-i
3525-find-x-value-of-array-ii
3550-smallest-index-with-digit-sum-equal-to-index
3568-minimum-moves-to-clean-the-classroom
3689-maximum-total-subarray-value-i
3718-smallest-missing-multiple-of-k
3833-count-dominant-indices
3834-merge-adjacent-equal-elements
3847-find-the-score-difference-in-a-game
3875-construct-uniform-parity-array-i
3876-construct-uniform-parity-array-ii
3903-smallest-stable-index-i
3904-smallest-stable-index-ii
3921-score-validator

Hash Table

0001-two-sum
0003-longest-substring-without-repeating-characters
0013-roman-to-integer
0036-valid-sudoku
0049-group-anagrams
0073-set-matrix-zeroes
0076-minimum-window-substring
0126-word-ladder-ii
0127-word-ladder
0169-majority-element
0202-happy-number
0205-isomorphic-strings
0217-contains-duplicate
0229-majority-element-ii
0242-valid-anagram
0347-top-k-frequent-elements
0424-longest-repeating-character-replacement
0560-subarray-sum-equals-k
0567-permutation-in-string
0645-set-mismatch
0961-n-repeated-element-in-size-2n-array
1096-brace-expansion-ii
1365-how-many-numbers-are-smaller-than-the-current-number
1477-find-two-non-overlapping-sub-arrays-each-with-target-sum
1520-maximum-number-of-non-overlapping-substrings
1658-minimum-operations-to-reduce-x-to-zero
1679-max-number-of-k-sum-pairs
1807-evaluate-the-bracket-pairs-of-a-string
1980-find-unique-binary-string
2094-finding-3-digit-even-numbers
2367-number-of-arithmetic-triplets
2441-largest-positive-integer-that-exists-with-its-negative
2932-maximum-strong-pair-xor-i
2958-length-of-longest-subarray-with-at-most-k-frequency
2996-smallest-missing-integer-greater-than-sequential-prefix-sum
3471-find-the-largest-almost-missing-integer
3483-unique-3-digit-even-numbers
3568-minimum-moves-to-clean-the-classroom
3718-smallest-missing-multiple-of-k
3760-maximum-substrings-with-distinct-start
3945-digit-frequency-score

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
0074-search-a-2d-matrix
0081-search-in-rotated-sorted-array-ii
0153-find-minimum-in-rotated-sorted-array
0162-find-peak-element
0167-two-sum-ii-input-array-is-sorted
0287-find-the-duplicate-number
0410-split-array-largest-sum
0493-reverse-pairs
0540-single-element-in-a-sorted-array
0704-binary-search
0875-koko-eating-bananas
1004-max-consecutive-ones-iii
1011-capacity-to-ship-packages-within-d-days
1095-find-in-mountain-array
1283-find-the-smallest-divisor-given-a-threshold
1351-count-negative-numbers-in-a-sorted-matrix
1477-find-two-non-overlapping-sub-arrays-each-with-target-sum
1482-minimum-number-of-days-to-make-m-bouquets
1539-kth-missing-positive-number
1658-minimum-operations-to-reduce-x-to-zero
1838-frequency-of-the-most-frequent-element
2333-minimum-sum-of-squared-difference
3414-maximum-score-of-non-overlapping-intervals
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
0347-top-k-frequent-elements
0493-reverse-pairs

Math

0002-add-two-numbers
0009-palindrome-number
0013-roman-to-integer
0048-rotate-image
0062-unique-paths
0066-plus-one
0070-climbing-stairs
0150-evaluate-reverse-polish-notation
0189-rotate-array
0202-happy-number
0224-basic-calculator
0258-add-digits
0326-power-of-three
0836-rectangle-overlap
1071-greatest-common-divisor-of-strings
1281-subtract-the-product-and-sum-of-digits-of-an-integer
1342-number-of-steps-to-reduce-a-number-to-zero
1401-circle-and-rectangle-overlapping
1523-count-odd-numbers-in-an-interval-range
1621-number-of-sets-of-k-non-overlapping-line-segments
1688-count-of-matches-in-tournament
1903-largest-odd-number-in-string
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
3014-minimum-number-of-pushes-to-type-word-i
3264-final-array-state-after-k-multiplication-operations-i
3524-find-x-value-of-array-i
3525-find-x-value-of-array-ii
3550-smallest-index-with-digit-sum-equal-to-index
3622-check-divisibility-by-digit-sum-and-product
3870-count-commas-in-range
3871-count-commas-in-range-ii
3875-construct-uniform-parity-array-i
3876-construct-uniform-parity-array-ii
3945-digit-frequency-score

Matrix

0036-valid-sudoku
0048-rotate-image
0054-spiral-matrix
0063-unique-paths-ii
0064-minimum-path-sum
0073-set-matrix-zeroes
0074-search-a-2d-matrix
0130-surrounded-regions
0200-number-of-islands
0542-01-matrix
0733-flood-fill
0835-image-overlap
0931-minimum-falling-path-sum
0994-rotting-oranges
1020-number-of-enclaves
1351-count-negative-numbers-in-a-sorted-matrix
1463-cherry-pickup-ii
1582-special-positions-in-a-binary-matrix
2267-check-if-there-is-a-valid-parentheses-string-path
3568-minimum-moves-to-clean-the-classroom

Sorting

0015-3sum
0016-3sum-closest
0018-4sum
0049-group-anagrams
0056-merge-intervals
0075-sort-colors
0088-merge-sorted-array
0169-majority-element
0217-contains-duplicate
0229-majority-element-ii
0242-valid-anagram
0347-top-k-frequent-elements
0455-assign-cookies
0645-set-mismatch
0853-car-fleet
1096-brace-expansion-ii
1365-how-many-numbers-are-smaller-than-the-current-number
1520-maximum-number-of-non-overlapping-substrings
1637-widest-vertical-area-between-two-points-containing-no-points
1679-max-number-of-k-sum-pairs
1838-frequency-of-the-most-frequent-element
2094-finding-3-digit-even-numbers
2160-minimum-sum-of-four-digit-number-after-splitting-digits
2333-minimum-sum-of-squared-difference
2344-minimum-deletions-to-make-array-divisible
2441-largest-positive-integer-that-exists-with-its-negative
2996-smallest-missing-integer-greater-than-sequential-prefix-sum
3414-maximum-score-of-non-overlapping-intervals
3467-transform-array-by-parity

Counting Sort

0169-majority-element
0229-majority-element-ii
0347-top-k-frequent-elements
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
0014-longest-common-prefix
0020-valid-parentheses
0022-generate-parentheses
0032-longest-valid-parentheses
0049-group-anagrams
0058-length-of-last-word
0076-minimum-window-substring
0115-distinct-subsequences
0125-valid-palindrome
0126-word-ladder-ii
0127-word-ladder
0151-reverse-words-in-a-string
0205-isomorphic-strings
0224-basic-calculator
0242-valid-anagram
0301-remove-invalid-parentheses
0344-reverse-string
0345-reverse-vowels-of-a-string
0392-is-subsequence
0424-longest-repeating-character-replacement
0557-reverse-words-in-a-string-iii
0567-permutation-in-string
0678-valid-parenthesis-string
0680-valid-palindrome-ii
0709-to-lower-case
0796-rotate-string
0856-score-of-parentheses
0921-minimum-add-to-make-parentheses-valid
0940-distinct-subsequences-ii
1021-remove-outermost-parentheses
1047-remove-all-adjacent-duplicates-in-string
1071-greatest-common-divisor-of-strings
1096-brace-expansion-ii
1108-defanging-an-ip-address
1111-maximum-nesting-depth-of-two-valid-parentheses-strings
1190-reverse-substrings-between-each-pair-of-parentheses
1520-maximum-number-of-non-overlapping-substrings
1541-minimum-insertions-to-balance-a-parentheses-string
1545-find-kth-bit-in-nth-binary-string
1614-maximum-nesting-depth-of-the-parentheses
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
1807-evaluate-the-bracket-pairs-of-a-string
1888-minimum-number-of-flips-to-make-the-binary-string-alternating
1903-largest-odd-number-in-string
1967-number-of-strings-that-appear-as-substrings-in-word
1980-find-unique-binary-string
2011-final-value-of-variable-after-performing-operations
2472-maximum-number-of-non-overlapping-palindrome-substrings
2904-shortest-and-lexicographically-smallest-beautiful-string
2942-find-words-containing-character
3014-minimum-number-of-pushes-to-type-word-i
3110-score-of-a-string
3760-maximum-substrings-with-distinct-start
3884-first-matching-character-from-both-ends
3921-score-validator

Stack

0020-valid-parentheses
0032-longest-valid-parentheses
0042-trapping-rain-water
0094-binary-tree-inorder-traversal
0114-flatten-binary-tree-to-linked-list
0144-binary-tree-preorder-traversal
0145-binary-tree-postorder-traversal
0150-evaluate-reverse-polish-notation
0155-min-stack
0224-basic-calculator
0225-implement-stack-using-queues
0232-implement-queue-using-stacks
0234-palindrome-linked-list
0678-valid-parenthesis-string
0739-daily-temperatures
0853-car-fleet
0856-score-of-parentheses
0921-minimum-add-to-make-parentheses-valid
1021-remove-outermost-parentheses
1047-remove-all-adjacent-duplicates-in-string
1096-brace-expansion-ii
1111-maximum-nesting-depth-of-two-valid-parentheses-strings
1190-reverse-substrings-between-each-pair-of-parentheses
1541-minimum-insertions-to-balance-a-parentheses-string
1614-maximum-nesting-depth-of-the-parentheses
3834-merge-adjacent-equal-elements

Two Pointers

0015-3sum
0016-3sum-closest
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
0167-two-sum-ii-input-array-is-sorted
0189-rotate-array
0202-happy-number
0234-palindrome-linked-list
0283-move-zeroes
0287-find-the-duplicate-number
0344-reverse-string
0345-reverse-vowels-of-a-string
0392-is-subsequence
0455-assign-cookies
0557-reverse-words-in-a-string-iii
0567-permutation-in-string
0680-valid-palindrome-ii
1679-max-number-of-k-sum-pairs
1768-merge-strings-alternately
2149-rearrange-array-elements-by-sign
2367-number-of-arithmetic-triplets
2396-strictly-palindromic-number
2441-largest-positive-integer-that-exists-with-its-negative
2472-maximum-number-of-non-overlapping-palindrome-substrings
3884-first-matching-character-from-both-ends

Greedy

0334-increasing-triplet-subsequence
0410-split-array-largest-sum
0455-assign-cookies
0678-valid-parenthesis-string
0680-valid-palindrome-ii
0860-lemonade-change
0921-minimum-add-to-make-parentheses-valid
1520-maximum-number-of-non-overlapping-substrings
1541-minimum-insertions-to-balance-a-parentheses-string
1689-partitioning-into-minimum-number-of-deci-binary-numbers
1838-frequency-of-the-most-frequent-element
1903-largest-odd-number-in-string
2160-minimum-sum-of-four-digit-number-after-splitting-digits
2333-minimum-sum-of-squared-difference
2472-maximum-number-of-non-overlapping-palindrome-substrings
2789-largest-element-in-an-array-after-merge-operations
3014-minimum-number-of-pushes-to-type-word-i
3600-maximize-spanning-tree-stability-with-upgrades
3689-maximum-total-subarray-value-i

Enumeration

1925-count-square-sum-triples
2094-finding-3-digit-even-numbers
2367-number-of-arithmetic-triplets
3483-unique-3-digit-even-numbers
3827-count-monobit-integers
3833-count-dominant-indices

Bit Manipulation

0287-find-the-duplicate-number
0645-set-mismatch
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
3568-minimum-moves-to-clean-the-classroom
3827-count-monobit-integers

Heap (Priority Queue)

0023-merge-k-sorted-lists
0239-sliding-window-maximum
0347-top-k-frequent-elements
2333-minimum-sum-of-squared-difference
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
1929-concatenation-of-array
2011-final-value-of-variable-after-performing-operations
2149-rearrange-array-elements-by-sign
2553-separate-the-digits-in-an-array
3264-final-array-state-after-k-multiplication-operations-i
3834-merge-adjacent-equal-elements
3847-find-the-score-difference-in-a-game
3921-score-validator

Brainteaser

2396-strictly-palindromic-number

Prefix Sum

0238-product-of-array-except-self
0410-split-array-largest-sum
0560-subarray-sum-equals-k
1004-max-consecutive-ones-iii
1621-number-of-sets-of-k-non-overlapping-line-segments
1658-minimum-operations-to-reduce-x-to-zero
1732-find-the-highest-altitude
1769-minimum-number-of-operations-to-move-all-balls-to-each-box
1838-frequency-of-the-most-frequent-element
2574-left-and-right-sum-differences
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
3903-smallest-stable-index-i
3904-smallest-stable-index-ii

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
2094-finding-3-digit-even-numbers
3483-unique-3-digit-even-numbers

Number Theory

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

Trie

0014-longest-common-prefix
2932-maximum-strong-pair-xor-i

Sliding Window

0003-longest-substring-without-repeating-characters
0076-minimum-window-substring
0239-sliding-window-maximum
0424-longest-repeating-character-replacement
0567-permutation-in-string
0643-maximum-average-subarray-i
1004-max-consecutive-ones-iii
1477-find-two-non-overlapping-sub-arrays-each-with-target-sum
1658-minimum-operations-to-reduce-x-to-zero
1838-frequency-of-the-most-frequent-element
1888-minimum-number-of-flips-to-make-the-binary-string-alternating
2401-longest-nice-subarray
2904-shortest-and-lexicographically-smallest-beautiful-string
2932-maximum-strong-pair-xor-i
2958-length-of-longest-subarray-with-at-most-k-frequency
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
0062-unique-paths
0063-unique-paths-ii
0064-minimum-path-sum
0070-climbing-stairs
0115-distinct-subsequences
0118-pascals-triangle
0120-triangle
0121-best-time-to-buy-and-sell-stock
0124-binary-tree-maximum-path-sum
0152-maximum-product-subarray
0198-house-robber
0213-house-robber-ii
0392-is-subsequence
0410-split-array-largest-sum
0416-partition-equal-subset-sum
0542-01-matrix
0678-valid-parenthesis-string
0746-min-cost-climbing-stairs
0931-minimum-falling-path-sum
0940-distinct-subsequences-ii
1463-cherry-pickup-ii
1477-find-two-non-overlapping-sub-arrays-each-with-target-sum
1621-number-of-sets-of-k-non-overlapping-line-segments
1888-minimum-number-of-flips-to-make-the-binary-string-alternating
2267-check-if-there-is-a-valid-parentheses-string-path
2472-maximum-number-of-non-overlapping-palindrome-substrings
3129-find-all-possible-stable-binary-arrays-i
3130-find-all-possible-stable-binary-arrays-ii
3414-maximum-score-of-non-overlapping-intervals
3524-find-x-value-of-array-i

Binary Indexed Tree

0493-reverse-pairs

Segment Tree

0493-reverse-pairs
3525-find-x-value-of-array-ii

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
2058-find-the-minimum-and-maximum-number-of-nodes-between-critical-points

Tree

0094-binary-tree-inorder-traversal
0100-same-tree
0102-binary-tree-level-order-traversal
0103-binary-tree-zigzag-level-order-traversal
0104-maximum-depth-of-binary-tree
0110-balanced-binary-tree
0114-flatten-binary-tree-to-linked-list
0124-binary-tree-maximum-path-sum
0129-sum-root-to-leaf-numbers
0144-binary-tree-preorder-traversal
0145-binary-tree-postorder-traversal
0199-binary-tree-right-side-view
0543-diameter-of-binary-tree
0700-search-in-a-binary-search-tree
2265-count-nodes-equal-to-average-of-subtree

Depth-First Search

0094-binary-tree-inorder-traversal
0100-same-tree
0104-maximum-depth-of-binary-tree
0110-balanced-binary-tree
0114-flatten-binary-tree-to-linked-list
0124-binary-tree-maximum-path-sum
0129-sum-root-to-leaf-numbers
0130-surrounded-regions
0144-binary-tree-preorder-traversal
0145-binary-tree-postorder-traversal
0199-binary-tree-right-side-view
0200-number-of-islands
0207-course-schedule
0543-diameter-of-binary-tree
0547-number-of-provinces
0733-flood-fill
0785-is-graph-bipartite
1020-number-of-enclaves
2265-count-nodes-equal-to-average-of-subtree

Binary Tree

0094-binary-tree-inorder-traversal
0100-same-tree
0102-binary-tree-level-order-traversal
0103-binary-tree-zigzag-level-order-traversal
0104-maximum-depth-of-binary-tree
0110-balanced-binary-tree
0114-flatten-binary-tree-to-linked-list
0124-binary-tree-maximum-path-sum
0129-sum-root-to-leaf-numbers
0144-binary-tree-preorder-traversal
0145-binary-tree-postorder-traversal
0199-binary-tree-right-side-view
0543-diameter-of-binary-tree
0700-search-in-a-binary-search-tree
2265-count-nodes-equal-to-average-of-subtree

Breadth-First Search

0100-same-tree
0102-binary-tree-level-order-traversal
0103-binary-tree-zigzag-level-order-traversal
0104-maximum-depth-of-binary-tree
0126-word-ladder-ii
0127-word-ladder
0130-surrounded-regions
0199-binary-tree-right-side-view
0200-number-of-islands
0207-course-schedule
0301-remove-invalid-parentheses
0542-01-matrix
0547-number-of-provinces
0733-flood-fill
0785-is-graph-bipartite
0994-rotting-oranges
1020-number-of-enclaves
1096-brace-expansion-ii
3568-minimum-moves-to-clean-the-classroom

Queue

0225-implement-stack-using-queues
0232-implement-queue-using-stacks
0239-sliding-window-maximum
3191-minimum-operations-to-make-binary-array-elements-equal-to-one-i

Design

0155-min-stack
0225-implement-stack-using-queues
0232-implement-queue-using-stacks

Union-Find

0130-surrounded-regions
0200-number-of-islands
0547-number-of-provinces
0785-is-graph-bipartite
1020-number-of-enclaves
3600-maximize-spanning-tree-stability-with-upgrades

Monotonic Stack

0042-trapping-rain-water
0739-daily-temperatures
0853-car-fleet

Backtracking

0022-generate-parentheses
0039-combination-sum
0046-permutations
0126-word-ladder-ii
0301-remove-invalid-parentheses
1096-brace-expansion-ii
1980-find-unique-binary-string

Interactive

1095-find-in-mountain-array

Database

0197-rising-temperature
0570-managers-with-at-least-5-direct-reports
0577-employee-bonus
0584-find-customer-referee
0595-big-countries
0596-classes-with-at-least-5-students
0610-triangle-judgement
0619-biggest-single-number
0620-not-boring-movies
1045-customers-who-bought-all-products
1068-product-sales-analysis-i
1070-product-sales-analysis-iii
1075-project-employees-i
1141-user-activity-for-the-past-30-days-i
1148-article-views-i
1174-immediate-food-delivery-ii
1193-monthly-transactions-i
1211-queries-quality-and-percentage
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
1633-percentage-of-users-attended-a-contest
1661-average-time-of-process-per-machine
1683-invalid-tweets
1729-find-followers-count
1789-primary-department-for-each-employee
1934-confirmation-rate
2356-number-of-unique-subjects-taught-by-each-teacher

Graph Theory

0207-course-schedule
0547-number-of-provinces
0785-is-graph-bipartite
3600-maximize-spanning-tree-stability-with-upgrades

Minimum Spanning Tree

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

Binary Search Tree

0700-search-in-a-binary-search-tree

Bucket Sort

0347-top-k-frequent-elements

Quickselect

0347-top-k-frequent-elements

Monotonic Queue

0239-sliding-window-maximum

Topological Sort

0207-course-schedule

Memoization

0070-climbing-stairs

Combinatorics

0062-unique-paths
1621-number-of-sets-of-k-non-overlapping-line-segments

Graph Coloring

0785-is-graph-bipartite

Bipartite Graph

0785-is-graph-bipartite

Directed Acyclic Graph

0207-course-schedule

Knapsack Problem

0416-partition-equal-subset-sum

0-1 Knapsack

0416-partition-equal-subset-sum

Bracket Sequences

0022-generate-parentheses
0032-longest-valid-parentheses
0678-valid-parenthesis-string
0856-score-of-parentheses
0921-minimum-add-to-make-parentheses-valid
1021-remove-outermost-parentheses
1111-maximum-nesting-depth-of-two-valid-parentheses-strings
1190-reverse-substrings-between-each-pair-of-parentheses
1541-minimum-insertions-to-balance-a-parentheses-string
1614-maximum-nesting-depth-of-the-parentheses
2267-check-if-there-is-a-valid-parentheses-string-path

String Matching

0796-rotate-string

DP on Trees

0124-binary-tree-maximum-path-sum

Geometry

0836-rectangle-overlap
1401-circle-and-rectangle-overlapping

Euclidean Algorithm

1071-greatest-common-divisor-of-strings

Greatest Common Divisor

1071-greatest-common-divisor-of-strings

Longest Increasing Subsequence

0334-increasing-triplet-subsequence

Boyer–Moore Majority Vote Algorithm

0169-majority-element