DSA and SQL Questions

Collection of LeetCode questions I have solved!

Array

0001-two-sum
0217-contains-duplicate
1044-find-common-characters
1528-kids-with-the-greatest-number-of-candies
1791-richest-customer-wealth
2454-largest-local-values-in-a-matrix
2519-find-the-original-array-of-prefix-xor
2696-the-number-of-beautiful-subsets
2876-number-of-employees-who-met-the-target
3194-find-words-containing-character

String

0242-valid-anagram
0344-reverse-string
0409-longest-palindrome
1044-find-common-characters
1797-goal-parser-interpretation
3194-find-words-containing-character

Matrix

1791-richest-customer-wealth
2454-largest-local-values-in-a-matrix

Hash Table

0001-two-sum
0217-contains-duplicate
0242-valid-anagram
0409-longest-palindrome
1044-find-common-characters

Greedy

0409-longest-palindrome

Bit Manipulation

2519-find-the-original-array-of-prefix-xor

Two Pointers

0344-reverse-string
2481-strictly-palindromic-number

Database

2495-number-of-unique-subjects-taught-by-each-teacher

Dynamic Programming

2696-the-number-of-beautiful-subsets

Backtracking

2696-the-number-of-beautiful-subsets

Sorting

0217-contains-duplicate
0242-valid-anagram
2696-the-number-of-beautiful-subsets

Math

2383-add-two-integers
2481-strictly-palindromic-number
2491-smallest-even-multiple

Number Theory

2491-smallest-even-multiple

Brainteaser

2481-strictly-palindromic-number

LeetCode Topics

Two Pointers

0005-longest-palindromic-substring
0011-container-with-most-water
0015-3sum
0026-remove-duplicates-from-sorted-array
0027-remove-element
0031-next-permutation
0042-trapping-rain-water
0080-remove-duplicates-from-sorted-array-ii
0088-merge-sorted-array
0151-reverse-words-in-a-string
0167-two-sum-ii-input-array-is-sorted
0189-rotate-array
0253-meeting-rooms-ii
0283-move-zeroes
0345-reverse-vowels-of-a-string
0392-is-subsequence
0443-string-compression
0567-permutation-in-string
1798-max-number-of-k-sum-pairs
1894-merge-strings-alternately
2216-delete-the-middle-node-of-a-linked-list
2236-maximum-twin-sum-of-a-linked-list

String

0003-longest-substring-without-repeating-characters
0005-longest-palindromic-substring
0008-string-to-integer-atoi
0012-integer-to-roman
0020-valid-parentheses
0022-generate-parentheses
0049-group-anagrams
0072-edit-distance
0076-minimum-window-substring
0079-word-search
0127-word-ladder
0151-reverse-words-in-a-string
0179-largest-number
0208-implement-trie-prefix-tree
0212-word-search-ii
0345-reverse-vowels-of-a-string
0392-is-subsequence
0394-decode-string
0412-fizz-buzz
0424-longest-repeating-character-replacement
0443-string-compression
0472-concatenated-words
0567-permutation-in-string
0649-dota2-senate
0778-reorganize-string
0952-word-subsets
1146-greatest-common-divisor-of-strings
1567-maximum-number-of-vowels-in-a-substring-of-given-length
1777-determine-if-two-strings-are-close
1894-merge-strings-alternately
2292-counting-words-with-a-given-prefix
2470-removing-stars-from-a-string
2520-using-a-robot-to-print-the-lexicographically-smallest-string
2727-number-of-senior-citizens
2839-check-if-strings-can-be-made-equal-with-operations-i

Math

0002-add-two-numbers
0009-palindrome-number
0012-integer-to-roman
0048-rotate-image
0062-unique-paths
0150-evaluate-reverse-polish-notation
0189-rotate-array
0268-missing-number
0380-insert-delete-getrandom-o1
0412-fizz-buzz
1146-greatest-common-divisor-of-strings

Array

0001-two-sum
0004-median-of-two-sorted-arrays
0011-container-with-most-water
0015-3sum
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
0036-valid-sudoku
0042-trapping-rain-water
0045-jump-game-ii
0048-rotate-image
0049-group-anagrams
0053-maximum-subarray
0054-spiral-matrix
0055-jump-game
0057-insert-interval
0074-search-a-2d-matrix
0079-word-search
0080-remove-duplicates-from-sorted-array-ii
0088-merge-sorted-array
0121-best-time-to-buy-and-sell-stock
0122-best-time-to-buy-and-sell-stock-ii
0128-longest-consecutive-sequence
0135-candy
0150-evaluate-reverse-polish-notation
0167-two-sum-ii-input-array-is-sorted
0169-majority-element
0179-largest-number
0189-rotate-array
0198-house-robber
0200-number-of-islands
0212-word-search-ii
0215-kth-largest-element-in-an-array
0217-contains-duplicate
0238-product-of-array-except-self
0239-sliding-window-maximum
0252-meeting-rooms
0253-meeting-rooms-ii
0268-missing-number
0283-move-zeroes
0322-coin-change
0334-increasing-triplet-subsequence
0347-top-k-frequent-elements
0380-insert-delete-getrandom-o1
0472-concatenated-words
0605-can-place-flowers
0643-maximum-average-subarray-i
0645-set-mismatch
0724-find-pivot-index
0733-flood-fill
0735-asteroid-collision
0739-daily-temperatures
0883-car-fleet
0907-koko-eating-bananas
0952-word-subsets
1036-rotting-oranges
1046-max-consecutive-ones-iii
1087-longest-arithmetic-subsequence
1108-analyze-user-website-visit-pattern
1239-largest-1-bordered-square
1319-unique-number-of-occurrences
1392-find-the-difference-of-two-arrays
1528-kids-with-the-greatest-number-of-candies
1586-longest-subarray-of-1s-after-deleting-one-element
1798-max-number-of-k-sum-pairs
1833-find-the-highest-altitude
2292-counting-words-with-a-given-prefix
2358-number-of-ways-to-split-array
2428-equal-row-and-column-pairs
2727-number-of-senior-citizens
3751-maximum-frequency-after-subarray-operation
3894-maximize-ysum-by-picking-a-triplet-of-distinct-xvalues

Greedy

0011-container-with-most-water
0045-jump-game-ii
0055-jump-game
0122-best-time-to-buy-and-sell-stock-ii
0135-candy
0179-largest-number
0253-meeting-rooms-ii
0334-increasing-triplet-subsequence
0605-can-place-flowers
0649-dota2-senate
0778-reorganize-string
2520-using-a-robot-to-print-the-lexicographically-smallest-string
3751-maximum-frequency-after-subarray-operation
3894-maximize-ysum-by-picking-a-triplet-of-distinct-xvalues

Prefix Sum

0238-product-of-array-except-self
0253-meeting-rooms-ii
0724-find-pivot-index
1046-max-consecutive-ones-iii
1833-find-the-highest-altitude
2358-number-of-ways-to-split-array
3751-maximum-frequency-after-subarray-operation

Dynamic Programming

0005-longest-palindromic-substring
0022-generate-parentheses
0042-trapping-rain-water
0045-jump-game-ii
0053-maximum-subarray
0055-jump-game
0062-unique-paths
0072-edit-distance
0121-best-time-to-buy-and-sell-stock
0122-best-time-to-buy-and-sell-stock-ii
0198-house-robber
0322-coin-change
0392-is-subsequence
0472-concatenated-words
1087-longest-arithmetic-subsequence
1239-largest-1-bordered-square
1474-longest-zigzag-path-in-a-binary-tree
1586-longest-subarray-of-1s-after-deleting-one-element
3751-maximum-frequency-after-subarray-operation

Hash Table

0001-two-sum
0003-longest-substring-without-repeating-characters
0012-integer-to-roman
0036-valid-sudoku
0049-group-anagrams
0076-minimum-window-substring
0127-word-ladder
0128-longest-consecutive-sequence
0138-copy-list-with-random-pointer
0146-lru-cache
0169-majority-element
0208-implement-trie-prefix-tree
0217-contains-duplicate
0268-missing-number
0347-top-k-frequent-elements
0380-insert-delete-getrandom-o1
0424-longest-repeating-character-replacement
0567-permutation-in-string
0645-set-mismatch
0778-reorganize-string
0952-word-subsets
1087-longest-arithmetic-subsequence
1108-analyze-user-website-visit-pattern
1319-unique-number-of-occurrences
1392-find-the-difference-of-two-arrays
1777-determine-if-two-strings-are-close
1798-max-number-of-k-sum-pairs
2428-equal-row-and-column-pairs
2520-using-a-robot-to-print-the-lexicographically-smallest-string
3751-maximum-frequency-after-subarray-operation
3894-maximize-ysum-by-picking-a-triplet-of-distinct-xvalues

Sorting

0015-3sum
0049-group-anagrams
0088-merge-sorted-array
0169-majority-element
0179-largest-number
0215-kth-largest-element-in-an-array
0217-contains-duplicate
0252-meeting-rooms
0253-meeting-rooms-ii
0268-missing-number
0347-top-k-frequent-elements
0645-set-mismatch
0778-reorganize-string
0883-car-fleet
1108-analyze-user-website-visit-pattern
1777-determine-if-two-strings-are-close
1798-max-number-of-k-sum-pairs
3894-maximize-ysum-by-picking-a-triplet-of-distinct-xvalues

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
1046-max-consecutive-ones-iii
1567-maximum-number-of-vowels-in-a-substring-of-given-length
1586-longest-subarray-of-1s-after-deleting-one-element

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
0074-search-a-2d-matrix
0167-two-sum-ii-input-array-is-sorted
0268-missing-number
0907-koko-eating-bananas
1046-max-consecutive-ones-iii
1087-longest-arithmetic-subsequence

Matrix

0036-valid-sudoku
0048-rotate-image
0054-spiral-matrix
0074-search-a-2d-matrix
0079-word-search
0200-number-of-islands
0212-word-search-ii
0733-flood-fill
1036-rotting-oranges
1239-largest-1-bordered-square
2428-equal-row-and-column-pairs

Simulation

0054-spiral-matrix
0412-fizz-buzz
0735-asteroid-collision
2428-equal-row-and-column-pairs
2470-removing-stars-from-a-string

Counting

0169-majority-element
0347-top-k-frequent-elements
0778-reorganize-string
1777-determine-if-two-strings-are-close

Stack

0020-valid-parentheses
0042-trapping-rain-water
0094-binary-tree-inorder-traversal
0150-evaluate-reverse-polish-notation
0155-min-stack
0394-decode-string
0735-asteroid-collision
0739-daily-temperatures
0883-car-fleet
2236-maximum-twin-sum-of-a-linked-list
2470-removing-stars-from-a-string
2520-using-a-robot-to-print-the-lexicographically-smallest-string

Recursion

0002-add-two-numbers
0021-merge-two-sorted-lists
0206-reverse-linked-list
0394-decode-string

Design

0146-lru-cache
0155-min-stack
0208-implement-trie-prefix-tree
0380-insert-delete-getrandom-o1
0969-number-of-recent-calls

Queue

0239-sliding-window-maximum
0649-dota2-senate
0969-number-of-recent-calls

Data Stream

0969-number-of-recent-calls

Database

0176-second-highest-salary
0178-rank-scores
0180-consecutive-numbers
0196-delete-duplicate-emails
0197-rising-temperature
0570-managers-with-at-least-5-direct-reports
0577-employee-bonus
0584-find-customer-referee
0585-investments-in-2016
0595-big-countries
0596-classes-more-than-5-students
0610-triangle-judgement
0619-biggest-single-number
0620-not-boring-movies
0626-exchange-seats
1135-customers-who-bought-all-products
1153-product-sales-analysis-i
1155-product-sales-analysis-iii
1161-project-employees-i
1182-game-play-analysis-iv
1245-user-activity-for-the-past-30-days-i
1258-article-views-i
1278-product-price-at-a-given-date
1292-immediate-food-delivery-ii
1317-monthly-transactions-i
1327-last-person-to-fit-in-the-bus
1338-queries-quality-and-percentage
1390-average-selling-price
1415-students-and-examinations
1452-restaurant-growth
1462-list-the-products-ordered-in-a-period
1480-movie-rating
1509-replace-employee-id-with-the-unique-identifier
1625-group-sold-products-by-the-date
1664-find-users-with-valid-e-mails
1670-patients-with-a-condition
1724-customer-who-visited-but-did-not-make-any-transactions
1773-percentage-of-users-attended-a-contest
1801-average-time-of-process-per-machine
1811-fix-names-in-a-table
1827-invalid-tweets
1877-find-followers-count
1882-the-number-of-employees-which-report-to-each-employee
1908-recyclable-and-low-fat-products
1942-primary-department-for-each-employee
2087-confirmation-rate
2127-employees-whose-manager-left-the-company
2495-number-of-unique-subjects-taught-by-each-teacher

Linked List

0002-add-two-numbers
0021-merge-two-sorted-lists
0023-merge-k-sorted-lists
0138-copy-list-with-random-pointer
0146-lru-cache
0206-reverse-linked-list
0328-odd-even-linked-list
2216-delete-the-middle-node-of-a-linked-list
2236-maximum-twin-sum-of-a-linked-list

Tree

0094-binary-tree-inorder-traversal
0102-binary-tree-level-order-traversal
0112-path-sum
0113-path-sum-ii
0199-binary-tree-right-side-view
0226-invert-binary-tree
0236-lowest-common-ancestor-of-a-binary-tree
0450-delete-node-in-a-bst
0783-search-in-a-binary-search-tree
0904-leaf-similar-trees
1116-maximum-level-sum-of-a-binary-tree
1474-longest-zigzag-path-in-a-binary-tree
1544-count-good-nodes-in-binary-tree

Depth-First Search

0079-word-search
0094-binary-tree-inorder-traversal
0112-path-sum
0113-path-sum-ii
0199-binary-tree-right-side-view
0200-number-of-islands
0207-course-schedule
0210-course-schedule-ii
0226-invert-binary-tree
0236-lowest-common-ancestor-of-a-binary-tree
0323-number-of-connected-components-in-an-undirected-graph
0472-concatenated-words
0733-flood-fill
0871-keys-and-rooms
0904-leaf-similar-trees
1116-maximum-level-sum-of-a-binary-tree
1474-longest-zigzag-path-in-a-binary-tree
1544-count-good-nodes-in-binary-tree

Binary Tree

0094-binary-tree-inorder-traversal
0102-binary-tree-level-order-traversal
0112-path-sum
0113-path-sum-ii
0199-binary-tree-right-side-view
0226-invert-binary-tree
0236-lowest-common-ancestor-of-a-binary-tree
0450-delete-node-in-a-bst
0783-search-in-a-binary-search-tree
0904-leaf-similar-trees
1116-maximum-level-sum-of-a-binary-tree
1474-longest-zigzag-path-in-a-binary-tree
1544-count-good-nodes-in-binary-tree

Breadth-First Search

0102-binary-tree-level-order-traversal
0112-path-sum
0127-word-ladder
0199-binary-tree-right-side-view
0200-number-of-islands
0207-course-schedule
0210-course-schedule-ii
0226-invert-binary-tree
0322-coin-change
0323-number-of-connected-components-in-an-undirected-graph
0733-flood-fill
0871-keys-and-rooms
1036-rotting-oranges
1116-maximum-level-sum-of-a-binary-tree
1544-count-good-nodes-in-binary-tree

String Matching

2292-counting-words-with-a-given-prefix

Backtracking

0022-generate-parentheses
0079-word-search
0113-path-sum-ii
0212-word-search-ii

Divide and Conquer

0004-median-of-two-sorted-arrays
0023-merge-k-sorted-lists
0053-maximum-subarray
0169-majority-element
0215-kth-largest-element-in-an-array
0347-top-k-frequent-elements

Monotonic Stack

0042-trapping-rain-water
0739-daily-temperatures
0883-car-fleet

Heap (Priority Queue)

0023-merge-k-sorted-lists
0215-kth-largest-element-in-an-array
0239-sliding-window-maximum
0253-meeting-rooms-ii
0347-top-k-frequent-elements
0778-reorganize-string
3894-maximize-ysum-by-picking-a-triplet-of-distinct-xvalues

Monotonic Queue

0239-sliding-window-maximum

Randomized

0380-insert-delete-getrandom-o1

Union Find

0128-longest-consecutive-sequence
0200-number-of-islands
0323-number-of-connected-components-in-an-undirected-graph

Enumeration

3751-maximum-frequency-after-subarray-operation

Doubly-Linked List

0146-lru-cache

Bucket Sort

0347-top-k-frequent-elements

Quickselect

0215-kth-largest-element-in-an-array
0347-top-k-frequent-elements

Merge Sort

0023-merge-k-sorted-lists

Graph

0207-course-schedule
0210-course-schedule-ii
0323-number-of-connected-components-in-an-undirected-graph
0871-keys-and-rooms

Topological Sort

0207-course-schedule
0210-course-schedule-ii

Combinatorics

0062-unique-paths

Trie

0208-implement-trie-prefix-tree
0212-word-search-ii
0472-concatenated-words

Bit Manipulation

0268-missing-number
0645-set-mismatch

Binary Search Tree

0450-delete-node-in-a-bst
0783-search-in-a-binary-search-tree