Algorithm

Programmers.
Level1.
Level2.

Baekjoon

Array

0026-remove-duplicates-from-sorted-array
0027-remove-element
0035-search-insert-position
0066-plus-one
0169-majority-element
0217-contains-duplicate
0268-missing-number
0283-move-zeroes
0346-moving-average-from-data-stream
0349-intersection-of-two-arrays
0455-assign-cookies
0463-island-perimeter
0645-set-mismatch
0661-image-smoother
1019-squares-of-a-sorted-array
1044-find-common-characters
1074-high-five
1217-relative-sort-array
1319-unique-number-of-occurrences
3242-count-elements-with-maximum-frequency

Two Pointers

0026-remove-duplicates-from-sorted-array
0027-remove-element
0028-find-the-index-of-the-first-occurrence-in-a-string
0125-valid-palindrome
0202-happy-number
0283-move-zeroes
0344-reverse-string
0349-intersection-of-two-arrays
0408-valid-word-abbreviation
0455-assign-cookies
0680-valid-palindrome-ii
1019-squares-of-a-sorted-array
1894-merge-strings-alternately

String

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

String Matching

0028-find-the-index-of-the-first-occurrence-in-a-string
0058-length-of-last-word
0067-add-binary
0125-valid-palindrome
0205-isomorphic-strings
0242-valid-anagram
0344-reverse-string
0387-first-unique-character-in-a-string
0408-valid-word-abbreviation
0409-longest-palindrome
0412-fizz-buzz
0415-add-strings
0680-valid-palindrome-ii
1044-find-common-characters
1146-greatest-common-divisor-of-strings
1894-merge-strings-alternately

Binary Search

0035-search-insert-position
0069-sqrtx

Math

0066-plus-one
0067-add-binary
0069-sqrtx
0202-happy-number
0231-power-of-two
0268-missing-number
0412-fizz-buzz
0415-add-strings
1146-greatest-common-divisor-of-strings
2383-add-two-integers

Bit Manipulation

0067-add-binary
0231-power-of-two
0268-missing-number
0645-set-mismatch

Simulation

0067-add-binary
0412-fizz-buzz
0415-add-strings

Hash Table

0169-majority-element
0202-happy-number
0205-isomorphic-strings
0217-contains-duplicate
0242-valid-anagram
0268-missing-number
0349-intersection-of-two-arrays
0359-logger-rate-limiter
0387-first-unique-character-in-a-string
0409-longest-palindrome
0645-set-mismatch
1044-find-common-characters
1074-high-five
1217-relative-sort-array
1319-unique-number-of-occurrences
3242-count-elements-with-maximum-frequency

Divide and Conquer

0169-majority-element

Sorting

0169-majority-element
0217-contains-duplicate
0242-valid-anagram
0268-missing-number
0349-intersection-of-two-arrays
0455-assign-cookies
0645-set-mismatch
1019-squares-of-a-sorted-array
1074-high-five
1217-relative-sort-array

Counting

0169-majority-element
0387-first-unique-character-in-a-string

Matrix

0463-island-perimeter
0661-image-smoother

Greedy

0409-longest-palindrome
0455-assign-cookies
0680-valid-palindrome-ii

Tree

0543-diameter-of-binary-tree
0975-range-sum-of-bst

Depth-First Search

0463-island-perimeter
0543-diameter-of-binary-tree
0975-range-sum-of-bst

Binary Search Tree

0268-missing-number
0349-intersection-of-two-arrays
0975-range-sum-of-bst

Binary Tree

0543-diameter-of-binary-tree
0975-range-sum-of-bst

Queue

0346-moving-average-from-data-stream
0387-first-unique-character-in-a-string

Design

0346-moving-average-from-data-stream
0359-logger-rate-limiter

Data Stream

0346-moving-average-from-data-stream
0359-logger-rate-limiter

Linked List

0206-reverse-linked-list

Recursion

0206-reverse-linked-list
0231-power-of-two

Counting Sort

1217-relative-sort-array
3242-count-elements-with-maximum-frequency

Breadth-First Search

0463-island-perimeter

Heap (Priority Queue)

1074-high-five

LeetCode Topics

Array

0001-two-sum
0011-container-with-most-water
0015-3sum
0039-combination-sum
0049-group-anagrams
0053-maximum-subarray
0054-spiral-matrix
0056-merge-intervals
0059-spiral-matrix-ii
0073-set-matrix-zeroes
0079-word-search
0088-merge-sorted-array
0121-best-time-to-buy-and-sell-stock
0128-longest-consecutive-sequence
0136-single-number
0152-maximum-product-subarray
0163-missing-ranges
0179-largest-number
0200-number-of-islands
0215-kth-largest-element-in-an-array
0219-contains-duplicate-ii
0228-summary-ranges
0238-product-of-array-except-self
0252-meeting-rooms
0268-missing-number
0271-encode-and-decode-strings
0322-coin-change
0347-top-k-frequent-elements
0350-intersection-of-two-arrays-ii
0380-insert-delete-getrandom-o1
0485-max-consecutive-ones
0496-next-greater-element-i
0560-subarray-sum-equals-k
0605-can-place-flowers
0628-maximum-product-of-three-numbers
0733-flood-fill
0777-toeplitz-matrix
0792-binary-search
0817-design-hashmap
0837-most-common-word
0890-lemonade-change
0898-transpose-matrix
1127-last-stone-weight
1256-rank-transform-of-an-array
1293-three-consecutive-odds
1306-minimum-absolute-difference
1382-calculate-amount-paid-in-taxes
1400-find-winner-on-a-tic-tac-toe-game
1496-lucky-numbers-in-a-matrix
1556-make-two-arrays-equal-by-reversing-subarrays
1603-running-sum-of-1d-array
1615-range-sum-of-sorted-subarray-sums
1646-kth-missing-positive-number
1720-crawler-log-folder
1730-special-array-with-x-elements-greater-than-or-equal-x
1741-sort-array-by-increasing-frequency
1755-defuse-the-bomb
1786-count-the-number-of-consistent-strings
1803-average-waiting-time
1829-maximum-units-on-a-truck
1878-check-if-array-is-sorted-and-rotated
2071-longest-common-subsequence-between-sorted-arrays
2132-convert-1d-array-into-2d-array
2148-minimum-number-of-moves-to-seat-everyone
2163-kth-distinct-string-in-an-array
2502-sort-the-people
2707-merge-two-2d-arrays-by-summing-values
2727-number-of-senior-citizens
3143-longest-unequal-adjacent-groups-subsequence-i
3227-find-missing-and-repeated-values
3469-maximum-height-of-a-triangle

Binary Search

0268-missing-number
0278-first-bad-version
0350-intersection-of-two-arrays-ii
0792-binary-search
1615-range-sum-of-sorted-subarray-sums
1646-kth-missing-positive-number
1730-special-array-with-x-elements-greater-than-or-equal-x

Sorting

0015-3sum
0049-group-anagrams
0056-merge-intervals
0088-merge-sorted-array
0179-largest-number
0215-kth-largest-element-in-an-array
0242-valid-anagram
0252-meeting-rooms
0268-missing-number
0314-binary-tree-vertical-order-traversal
0347-top-k-frequent-elements
0350-intersection-of-two-arrays-ii
0628-maximum-product-of-three-numbers
1256-rank-transform-of-an-array
1306-minimum-absolute-difference
1556-make-two-arrays-equal-by-reversing-subarrays
1615-range-sum-of-sorted-subarray-sums
1730-special-array-with-x-elements-greater-than-or-equal-x
1741-sort-array-by-increasing-frequency
1829-maximum-units-on-a-truck
2148-minimum-number-of-moves-to-seat-everyone
2327-largest-number-after-digit-swaps-by-parity
2502-sort-the-people

Hash Table

0001-two-sum
0003-longest-substring-without-repeating-characters
0049-group-anagrams
0073-set-matrix-zeroes
0128-longest-consecutive-sequence
0141-linked-list-cycle
0146-lru-cache
0208-implement-trie-prefix-tree
0219-contains-duplicate-ii
0242-valid-anagram
0268-missing-number
0314-binary-tree-vertical-order-traversal
0347-top-k-frequent-elements
0350-intersection-of-two-arrays-ii
0380-insert-delete-getrandom-o1
0383-ransom-note
0424-longest-repeating-character-replacement
0496-next-greater-element-i
0560-subarray-sum-equals-k
0782-jewels-and-stones
0817-design-hashmap
0837-most-common-word
0920-uncommon-words-from-two-sentences
1256-rank-transform-of-an-array
1400-find-winner-on-a-tic-tac-toe-game
1556-make-two-arrays-equal-by-reversing-subarrays
1741-sort-array-by-increasing-frequency
1786-count-the-number-of-consistent-strings
2071-longest-common-subsequence-between-sorted-arrays
2163-kth-distinct-string-in-an-array
2502-sort-the-people
2707-merge-two-2d-arrays-by-summing-values
3227-find-missing-and-repeated-values
3343-count-numbers-with-unique-digits-ii

Sliding Window

0003-longest-substring-without-repeating-characters
0219-contains-duplicate-ii
0424-longest-repeating-character-replacement
1755-defuse-the-bomb

Two Pointers

0011-container-with-most-water
0015-3sum
0088-merge-sorted-array
0125-valid-palindrome
0141-linked-list-cycle
0345-reverse-vowels-of-a-string
0350-intersection-of-two-arrays-ii
0647-palindromic-substrings
0908-middle-of-the-linked-list
1615-range-sum-of-sorted-subarray-sums
2707-merge-two-2d-arrays-by-summing-values

Tree

0230-kth-smallest-element-in-a-bst
0314-binary-tree-vertical-order-traversal
0789-kth-largest-element-in-a-stream

Depth-First Search

0200-number-of-islands
0211-design-add-and-search-words-data-structure
0230-kth-smallest-element-in-a-bst
0314-binary-tree-vertical-order-traversal
0733-flood-fill

Breadth-First Search

0200-number-of-islands
0314-binary-tree-vertical-order-traversal
0322-coin-change
0733-flood-fill

Binary Tree

0230-kth-smallest-element-in-a-bst
0314-binary-tree-vertical-order-traversal
0789-kth-largest-element-in-a-stream

Linked List

0021-merge-two-sorted-lists
0083-remove-duplicates-from-sorted-list
0141-linked-list-cycle
0146-lru-cache
0206-reverse-linked-list
0817-design-hashmap
0908-middle-of-the-linked-list

Design

0146-lru-cache
0208-implement-trie-prefix-tree
0211-design-add-and-search-words-data-structure
0271-encode-and-decode-strings
0380-insert-delete-getrandom-o1
0789-kth-largest-element-in-a-stream
0817-design-hashmap
1708-design-parking-system

Doubly-Linked List

0146-lru-cache

String

0003-longest-substring-without-repeating-characters
0020-valid-parentheses
0049-group-anagrams
0079-word-search
0125-valid-palindrome
0168-excel-sheet-column-title
0179-largest-number
0208-implement-trie-prefix-tree
0211-design-add-and-search-words-data-structure
0227-basic-calculator-ii
0242-valid-anagram
0271-encode-and-decode-strings
0345-reverse-vowels-of-a-string
0383-ransom-note
0424-longest-repeating-character-replacement
0647-palindromic-substrings
0782-jewels-and-stones
0812-rotate-string
0837-most-common-word
0851-goat-latin
0920-uncommon-words-from-two-sentences
1128-remove-all-adjacent-duplicates-in-string
1298-reverse-substrings-between-each-pair-of-parentheses
1302-delete-characters-to-make-fancy-string
1371-minimum-remove-to-make-valid-parentheses
1720-crawler-log-folder
1786-count-the-number-of-consistent-strings
1818-maximum-score-from-removing-substrings
2076-sum-of-digits-of-string-after-convert
2163-kth-distinct-string-in-an-array
2502-sort-the-people
2727-number-of-senior-citizens
2800-minimum-string-length-after-removing-substrings
3143-longest-unequal-adjacent-groups-subsequence-i
3379-score-of-a-string

Stack

0020-valid-parentheses
0227-basic-calculator-ii
0496-next-greater-element-i
1128-remove-all-adjacent-duplicates-in-string
1298-reverse-substrings-between-each-pair-of-parentheses
1371-minimum-remove-to-make-valid-parentheses
1720-crawler-log-folder
1818-maximum-score-from-removing-substrings
2800-minimum-string-length-after-removing-substrings

Union Find

0128-longest-consecutive-sequence
0200-number-of-islands

Matrix

0054-spiral-matrix
0059-spiral-matrix-ii
0073-set-matrix-zeroes
0079-word-search
0200-number-of-islands
0733-flood-fill
0777-toeplitz-matrix
0898-transpose-matrix
1400-find-winner-on-a-tic-tac-toe-game
1496-lucky-numbers-in-a-matrix
2132-convert-1d-array-into-2d-array
3227-find-missing-and-repeated-values

Math

0062-unique-paths
0070-climbing-stairs
0168-excel-sheet-column-title
0227-basic-calculator-ii
0258-add-digits
0268-missing-number
0380-insert-delete-getrandom-o1
0628-maximum-product-of-three-numbers
1642-water-bottles
2645-pass-the-pillow
3227-find-missing-and-repeated-values
3343-count-numbers-with-unique-digits-ii

Simulation

0054-spiral-matrix
0059-spiral-matrix-ii
0258-add-digits
0898-transpose-matrix
1382-calculate-amount-paid-in-taxes
1400-find-winner-on-a-tic-tac-toe-game
1642-water-bottles
1708-design-parking-system
1803-average-waiting-time
2076-sum-of-digits-of-string-after-convert
2132-convert-1d-array-into-2d-array
2645-pass-the-pillow
2800-minimum-string-length-after-removing-substrings

Divide and Conquer

0053-maximum-subarray
0191-number-of-1-bits
0215-kth-largest-element-in-an-array
0347-top-k-frequent-elements

Bit Manipulation

0136-single-number
0191-number-of-1-bits
0268-missing-number
0338-counting-bits
0476-number-complement
1786-count-the-number-of-consistent-strings
2323-minimum-bit-flips-to-convert-number

Heap (Priority Queue)

0215-kth-largest-element-in-an-array
0347-top-k-frequent-elements
0789-kth-largest-element-in-a-stream
1127-last-stone-weight
2327-largest-number-after-digit-swaps-by-parity

Bucket Sort

0347-top-k-frequent-elements

Counting

0347-top-k-frequent-elements
0383-ransom-note
0837-most-common-word
0920-uncommon-words-from-two-sentences
1708-design-parking-system
1786-count-the-number-of-consistent-strings
2071-longest-common-subsequence-between-sorted-arrays
2163-kth-distinct-string-in-an-array

Quickselect

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

Binary Search Tree

0230-kth-smallest-element-in-a-bst
0789-kth-largest-element-in-a-stream

Dynamic Programming

0053-maximum-subarray
0062-unique-paths
0070-climbing-stairs
0121-best-time-to-buy-and-sell-stock
0152-maximum-product-subarray
0322-coin-change
0338-counting-bits
0647-palindromic-substrings
3143-longest-unequal-adjacent-groups-subsequence-i
3343-count-numbers-with-unique-digits-ii

Memoization

0070-climbing-stairs

Prefix Sum

0238-product-of-array-except-self
0560-subarray-sum-equals-k
1603-running-sum-of-1d-array

Backtracking

0039-combination-sum
0079-word-search

Trie

0208-implement-trie-prefix-tree
0211-design-add-and-search-words-data-structure

Greedy

0011-container-with-most-water
0179-largest-number
0605-can-place-flowers
0890-lemonade-change
1818-maximum-score-from-removing-substrings
1829-maximum-units-on-a-truck
2148-minimum-number-of-moves-to-seat-everyone
3143-longest-unequal-adjacent-groups-subsequence-i

Recursion

0021-merge-two-sorted-lists
0206-reverse-linked-list

Combinatorics

0062-unique-paths

String Matching

0812-rotate-string

Counting Sort

2148-minimum-number-of-moves-to-seat-everyone

Hash Function

0817-design-hashmap

Data Stream

0789-kth-largest-element-in-a-stream

Graph

1916-find-center-of-star-graph

Interactive

0278-first-bad-version

Enumeration

3469-maximum-height-of-a-triangle

Number Theory

0258-add-digits

Monotonic Stack

0496-next-greater-element-i

Randomized

0380-insert-delete-getrandom-o1