LeetCode Topics

Array

0001-two-sum
0004-median-of-two-sorted-arrays
0015-3sum
0018-4sum
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
0035-search-insert-position
0039-combination-sum
0040-combination-sum-ii
0048-rotate-image
0051-n-queens
0053-maximum-subarray
0054-spiral-matrix
0056-merge-intervals
0066-plus-one
0073-set-matrix-zeroes
0074-search-a-2d-matrix
0075-sort-colors
0078-subsets
0079-word-search
0081-search-in-rotated-sorted-array-ii
0088-merge-sorted-array
0090-subsets-ii
0118-pascals-triangle
0119-pascals-triangle-ii
0121-best-time-to-buy-and-sell-stock
0128-longest-consecutive-sequence
0136-single-number
0137-single-number-ii
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
0204-count-primes
0216-combination-sum-iii
0217-contains-duplicate
0219-contains-duplicate-ii
0229-majority-element-ii
0238-product-of-array-except-self
0240-search-a-2d-matrix-ii
0260-single-number-iii
0268-missing-number
0283-move-zeroes
0287-find-the-duplicate-number
0349-intersection-of-two-arrays
0350-intersection-of-two-arrays-ii
0410-split-array-largest-sum
0414-third-maximum-number
0455-assign-cookies
0472-concatenated-words
0485-max-consecutive-ones
0493-reverse-pairs
0540-single-element-in-a-sorted-array
0560-subarray-sum-equals-k
0594-longest-harmonious-subsequence
0628-maximum-product-of-three-numbers
0645-set-mismatch
0748-largest-number-at-least-twice-of-others
0792-binary-search
0808-number-of-matching-subsequences
0907-koko-eating-bananas
0940-fruit-into-baskets
0981-delete-columns-to-make-sorted
1046-max-consecutive-ones-iii
1056-capacity-to-ship-packages-within-d-days
1306-minimum-absolute-difference
1408-find-the-smallest-divisor-given-a-threshold
1421-find-numbers-with-even-number-of-digits
1510-find-lucky-integer-in-an-array
1538-maximum-points-you-can-obtain-from-cards
1605-minimum-number-of-days-to-make-m-bouquets
1621-number-of-subsequences-that-satisfy-the-given-sum-condition
1646-kth-missing-positive-number
1675-magnetic-force-between-two-balls
1781-check-if-two-string-arrays-are-equivalent
1878-check-if-array-is-sorted-and-rotated
1966-frequency-of-the-most-frequent-element
1995-finding-pairs-with-a-certain-sum
2047-find-a-peak-element-ii
2248-minimum-cost-of-buying-candies-with-discount
2271-rearrange-array-elements-by-sign
2316-count-hills-and-valleys-in-an-array
2737-row-with-maximum-ones
3227-find-missing-and-repeated-values
3321-type-of-triangle
3490-find-the-maximum-length-of-valid-subsequence-i
3788-maximum-unique-subarray-sum-after-deletion
3790-fruits-into-baskets-ii

Hash Table

0001-two-sum
0003-longest-substring-without-repeating-characters
0012-integer-to-roman
0013-roman-to-integer
0017-letter-combinations-of-a-phone-number
0073-set-matrix-zeroes
0128-longest-consecutive-sequence
0138-copy-list-with-random-pointer
0141-linked-list-cycle
0142-linked-list-cycle-ii
0160-intersection-of-two-linked-lists
0169-majority-element
0202-happy-number
0205-isomorphic-strings
0217-contains-duplicate
0219-contains-duplicate-ii
0229-majority-element-ii
0242-valid-anagram
0268-missing-number
0290-word-pattern
0349-intersection-of-two-arrays
0350-intersection-of-two-arrays-ii
0383-ransom-note
0387-first-unique-character-in-a-string
0389-find-the-difference
0409-longest-palindrome
0451-sort-characters-by-frequency
0560-subarray-sum-equals-k
0594-longest-harmonious-subsequence
0645-set-mismatch
0808-number-of-matching-subsequences
0889-buddy-strings
0940-fruit-into-baskets
1460-number-of-substrings-containing-all-three-characters
1510-find-lucky-integer-in-an-array
1777-determine-if-two-strings-are-close
1890-sum-of-beauty-of-all-substrings
1960-check-if-the-sentence-is-pangram
1995-finding-pairs-with-a-certain-sum
2059-unique-length-3-palindromic-subsequences
3227-find-missing-and-repeated-values
3788-maximum-unique-subarray-sum-after-deletion

Math

0002-add-two-numbers
0007-reverse-integer
0009-palindrome-number
0012-integer-to-roman
0013-roman-to-integer
0029-divide-two-integers
0048-rotate-image
0050-powx-n
0060-permutation-sequence
0066-plus-one
0069-sqrtx
0189-rotate-array
0202-happy-number
0204-count-primes
0231-power-of-two
0268-missing-number
0326-power-of-three
0342-power-of-four
0628-maximum-product-of-three-numbers
0935-orderly-queue
1013-fibonacci-number
1411-convert-binary-number-in-a-linked-list-to-integer
1421-find-numbers-with-even-number-of-digits
1610-xor-operation-in-an-array
1885-count-number-of-homogenous-substrings
2032-largest-odd-number-in-string
2050-count-good-numbers
3172-divisible-and-non-divisible-sums-difference
3227-find-missing-and-repeated-values
3321-type-of-triangle

Two Pointers

0005-longest-palindromic-substring
0015-3sum
0018-4sum
0019-remove-nth-node-from-end-of-list
0026-remove-duplicates-from-sorted-array
0027-remove-element
0028-find-the-index-of-the-first-occurrence-in-a-string
0031-next-permutation
0061-rotate-list
0075-sort-colors
0082-remove-duplicates-from-sorted-list-ii
0088-merge-sorted-array
0125-valid-palindrome
0141-linked-list-cycle
0142-linked-list-cycle-ii
0148-sort-list
0151-reverse-words-in-a-string
0160-intersection-of-two-linked-lists
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
0349-intersection-of-two-arrays
0350-intersection-of-two-arrays-ii
0392-is-subsequence
0443-string-compression
0455-assign-cookies
0557-reverse-words-in-a-string-iii
0874-backspace-string-compare
0908-middle-of-the-linked-list
1621-number-of-subsequences-that-satisfy-the-given-sum-condition
2216-delete-the-middle-node-of-a-linked-list
2271-rearrange-array-elements-by-sign

Sorting

0015-3sum
0018-4sum
0056-merge-intervals
0075-sort-colors
0088-merge-sorted-array
0148-sort-list
0169-majority-element
0217-contains-duplicate
0229-majority-element-ii
0242-valid-anagram
0268-missing-number
0349-intersection-of-two-arrays
0350-intersection-of-two-arrays-ii
0389-find-the-difference
0414-third-maximum-number
0451-sort-characters-by-frequency
0455-assign-cookies
0594-longest-harmonious-subsequence
0628-maximum-product-of-three-numbers
0645-set-mismatch
0748-largest-number-at-least-twice-of-others
0808-number-of-matching-subsequences
0935-orderly-queue
1306-minimum-absolute-difference
1621-number-of-subsequences-that-satisfy-the-given-sum-condition
1675-magnetic-force-between-two-balls
1777-determine-if-two-strings-are-close
1966-frequency-of-the-most-frequent-element
2248-minimum-cost-of-buying-candies-with-discount
2887-sort-vowels-in-a-string
3321-type-of-triangle

Linked List

0002-add-two-numbers
0019-remove-nth-node-from-end-of-list
0021-merge-two-sorted-lists
0024-swap-nodes-in-pairs
0025-reverse-nodes-in-k-group
0061-rotate-list
0082-remove-duplicates-from-sorted-list-ii
0083-remove-duplicates-from-sorted-list
0138-copy-list-with-random-pointer
0141-linked-list-cycle
0142-linked-list-cycle-ii
0148-sort-list
0160-intersection-of-two-linked-lists
0203-remove-linked-list-elements
0206-reverse-linked-list
0234-palindrome-linked-list
0237-delete-node-in-a-linked-list
0328-odd-even-linked-list
0908-middle-of-the-linked-list
1411-convert-binary-number-in-a-linked-list-to-integer
2216-delete-the-middle-node-of-a-linked-list

String

0003-longest-substring-without-repeating-characters
0005-longest-palindromic-substring
0008-string-to-integer-atoi
0012-integer-to-roman
0013-roman-to-integer
0014-longest-common-prefix
0017-letter-combinations-of-a-phone-number
0020-valid-parentheses
0022-generate-parentheses
0028-find-the-index-of-the-first-occurrence-in-a-string
0038-count-and-say
0079-word-search
0093-restore-ip-addresses
0125-valid-palindrome
0131-palindrome-partitioning
0151-reverse-words-in-a-string
0205-isomorphic-strings
0242-valid-anagram
0290-word-pattern
0316-remove-duplicate-letters
0383-ransom-note
0387-first-unique-character-in-a-string
0389-find-the-difference
0392-is-subsequence
0409-longest-palindrome
0443-string-compression
0451-sort-characters-by-frequency
0459-repeated-substring-pattern
0472-concatenated-words
0520-detect-capital
0557-reverse-words-in-a-string-iii
0808-number-of-matching-subsequences
0812-rotate-string
0874-backspace-string-compare
0889-buddy-strings
0916-decoded-string-at-index
0935-orderly-queue
0981-delete-columns-to-make-sorted
1078-remove-outermost-parentheses
1159-smallest-subsequence-of-distinct-characters
1460-number-of-substrings-containing-all-three-characters
1666-make-the-string-great
1737-maximum-nesting-depth-of-the-parentheses
1777-determine-if-two-strings-are-close
1781-check-if-two-string-arrays-are-equivalent
1823-determine-if-string-halves-are-alike
1885-count-number-of-homogenous-substrings
1890-sum-of-beauty-of-all-substrings
1960-check-if-the-sentence-is-pangram
2032-largest-odd-number-in-string
2059-unique-length-3-palindromic-subsequences
2887-sort-vowels-in-a-string
3396-valid-word
3447-clear-digits
3617-find-the-original-typed-string-i
3931-process-string-with-special-operations-i

Stack

0020-valid-parentheses
0225-implement-stack-using-queues
0232-implement-queue-using-stacks
0234-palindrome-linked-list
0316-remove-duplicate-letters
0874-backspace-string-compare
0916-decoded-string-at-index
1078-remove-outermost-parentheses
1159-smallest-subsequence-of-distinct-characters
1666-make-the-string-great
1737-maximum-nesting-depth-of-the-parentheses
3447-clear-digits

Recursion

0002-add-two-numbers
0021-merge-two-sorted-lists
0024-swap-nodes-in-pairs
0025-reverse-nodes-in-k-group
0050-powx-n
0060-permutation-sequence
0203-remove-linked-list-elements
0206-reverse-linked-list
0231-power-of-two
0234-palindrome-linked-list
0326-power-of-three
0342-power-of-four
1013-fibonacci-number
2050-count-good-numbers

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
0069-sqrtx
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
0240-search-a-2d-matrix-ii
0268-missing-number
0287-find-the-duplicate-number
0349-intersection-of-two-arrays
0350-intersection-of-two-arrays-ii
0410-split-array-largest-sum
0493-reverse-pairs
0540-single-element-in-a-sorted-array
0792-binary-search
0808-number-of-matching-subsequences
0907-koko-eating-bananas
1046-max-consecutive-ones-iii
1056-capacity-to-ship-packages-within-d-days
1408-find-the-smallest-divisor-given-a-threshold
1605-minimum-number-of-days-to-make-m-bouquets
1621-number-of-subsequences-that-satisfy-the-given-sum-condition
1646-kth-missing-positive-number
1675-magnetic-force-between-two-balls
1966-frequency-of-the-most-frequent-element
2047-find-a-peak-element-ii
3790-fruits-into-baskets-ii

Matrix

0048-rotate-image
0054-spiral-matrix
0073-set-matrix-zeroes
0074-search-a-2d-matrix
0079-word-search
0240-search-a-2d-matrix-ii
2047-find-a-peak-element-ii
2737-row-with-maximum-ones
3227-find-missing-and-repeated-values

Divide and Conquer

0004-median-of-two-sorted-arrays
0053-maximum-subarray
0148-sort-list
0169-majority-element
0191-number-of-1-bits
0240-search-a-2d-matrix-ii
0493-reverse-pairs

Dynamic Programming

0005-longest-palindromic-substring
0022-generate-parentheses
0053-maximum-subarray
0118-pascals-triangle
0119-pascals-triangle-ii
0121-best-time-to-buy-and-sell-stock
0131-palindrome-partitioning
0152-maximum-product-subarray
0392-is-subsequence
0410-split-array-largest-sum
0472-concatenated-words
0808-number-of-matching-subsequences
1013-fibonacci-number
3490-find-the-maximum-length-of-valid-subsequence-i

Simulation

0054-spiral-matrix
0874-backspace-string-compare
2271-rearrange-array-elements-by-sign
3447-clear-digits
3790-fruits-into-baskets-ii
3931-process-string-with-special-operations-i

Union Find

0128-longest-consecutive-sequence

Bit Manipulation

0029-divide-two-integers
0078-subsets
0090-subsets-ii
0136-single-number
0137-single-number-ii
0191-number-of-1-bits
0231-power-of-two
0260-single-number-iii
0268-missing-number
0287-find-the-duplicate-number
0342-power-of-four
0389-find-the-difference
0645-set-mismatch
1610-xor-operation-in-an-array
2059-unique-length-3-palindromic-subsequences
2323-minimum-bit-flips-to-convert-number

Counting

0169-majority-element
0229-majority-element-ii
0383-ransom-note
0387-first-unique-character-in-a-string
0451-sort-characters-by-frequency
0594-longest-harmonious-subsequence
1510-find-lucky-integer-in-an-array
1777-determine-if-two-strings-are-close
1823-determine-if-string-halves-are-alike
1890-sum-of-beauty-of-all-substrings

Design

0225-implement-stack-using-queues
0232-implement-queue-using-stacks
1995-finding-pairs-with-a-certain-sum

Queue

0225-implement-stack-using-queues
0232-implement-queue-using-stacks
0387-first-unique-character-in-a-string

Greedy

0316-remove-duplicate-letters
0409-longest-palindrome
0410-split-array-largest-sum
0455-assign-cookies
1159-smallest-subsequence-of-distinct-characters
1966-frequency-of-the-most-frequent-element
2032-largest-odd-number-in-string
2248-minimum-cost-of-buying-candies-with-discount
3788-maximum-unique-subarray-sum-after-deletion

Memoization

1013-fibonacci-number

Prefix Sum

0238-product-of-array-except-self
0410-split-array-largest-sum
0560-subarray-sum-equals-k
1046-max-consecutive-ones-iii
1538-maximum-points-you-can-obtain-from-cards
1966-frequency-of-the-most-frequent-element
2059-unique-length-3-palindromic-subsequences

Sliding Window

0003-longest-substring-without-repeating-characters
0219-contains-duplicate-ii
0594-longest-harmonious-subsequence
0940-fruit-into-baskets
1046-max-consecutive-ones-iii
1460-number-of-substrings-containing-all-three-characters
1538-maximum-points-you-can-obtain-from-cards
1966-frequency-of-the-most-frequent-element

Binary Indexed Tree

0493-reverse-pairs

Segment Tree

0493-reverse-pairs
3790-fruits-into-baskets-ii

Merge Sort

0148-sort-list
0493-reverse-pairs

Ordered Set

0493-reverse-pairs
3790-fruits-into-baskets-ii

Trie

0014-longest-common-prefix
0472-concatenated-words
0808-number-of-matching-subsequences

String Matching

0028-find-the-index-of-the-first-occurrence-in-a-string
0459-repeated-substring-pattern
0812-rotate-string

Heap (Priority Queue)

0451-sort-characters-by-frequency

Bucket Sort

0451-sort-characters-by-frequency

Backtracking

0017-letter-combinations-of-a-phone-number
0022-generate-parentheses
0039-combination-sum
0040-combination-sum-ii
0051-n-queens
0078-subsets
0079-word-search
0090-subsets-ii
0093-restore-ip-addresses
0131-palindrome-partitioning
0216-combination-sum-iii

Depth-First Search

0079-word-search
0472-concatenated-words

Monotonic Stack

0316-remove-duplicate-letters
1159-smallest-subsequence-of-distinct-characters

Enumeration

0204-count-primes

Number Theory

0204-count-primes