LeetCode Notes

This repository contains my LeetCode problem solutions.

The goal is to keep track of problems I have solved and the concepts I am learning. It also acts as a place for quick revision.

Solutions are added as I practice. Code quality and optimization may vary.

This repository is for personal learning and reference.

now also has the solution from the placement training

prompt

Create markdown file for the given problem. include the leetcode number, problem link, write the brute force and optimized solution. explain the flow of the algorithm using an example. explain the core idea and thinking view. include the intuvtion. include the images if possible from the internet.

LeetCode Topics

Array

0001-two-sum
0011-container-with-most-water
0014-longest-common-prefix
0015-3sum
0031-next-permutation
0033-search-in-rotated-sorted-array
0039-combination-sum
0040-combination-sum-ii
0045-jump-game-ii
0046-permutations
0048-rotate-image
0049-group-anagrams
0053-maximum-subarray
0054-spiral-matrix
0056-merge-intervals
0073-set-matrix-zeroes
0074-search-a-2d-matrix
0075-sort-colors
0078-subsets
0079-word-search
0088-merge-sorted-array
0090-subsets-ii
0118-pascals-triangle
0121-best-time-to-buy-and-sell-stock
0128-longest-consecutive-sequence
0136-single-number
0152-maximum-product-subarray
0153-find-minimum-in-rotated-sorted-array
0154-find-minimum-in-rotated-sorted-array-ii
0167-two-sum-ii-input-array-is-sorted
0169-majority-element
0189-rotate-array
0204-count-primes
0209-minimum-size-subarray-sum
0217-contains-duplicate
0219-contains-duplicate-ii
0229-majority-element-ii
0238-product-of-array-except-self
0283-move-zeroes
0287-find-the-duplicate-number
0303-range-sum-query-immutable
0396-rotate-function
0448-find-all-numbers-disappeared-in-an-array
0493-reverse-pairs
0594-longest-harmonious-subsequence
0643-maximum-average-subarray-i
0682-baseball-game
0713-subarray-product-less-than-k
0745-find-smallest-letter-greater-than-target
0792-binary-search
0875-longest-mountain-in-array
0906-walking-robot-simulation
1019-squares-of-a-sorted-array
1036-rotting-oranges
1306-minimum-absolute-difference
1392-find-the-difference-of-two-arrays
1395-minimum-time-visiting-all-points
1447-jump-game-iv
1466-jump-game-v
1482-how-many-numbers-are-smaller-than-the-current-number
1507-check-if-there-is-a-valid-path-in-a-grid
1663-detect-cycles-in-2d-grid
1716-maximum-non-negative-product-in-a-matrix
1793-minimum-moves-to-make-array-complementary
1840-minimize-hamming-distance-after-swap-operations
1845-largest-submatrix-with-rearrangements
1878-check-if-array-is-sorted-and-rotated
1956-maximum-element-after-decreasing-and-rearranging
1961-maximum-ice-cream-bars
1968-maximum-building-height
1972-rotating-the-box
1984-maximum-distance-between-a-pair-of-values
2099-number-of-strings-that-appear-as-substrings-in-word
2137-final-value-of-variable-after-performing-operations
2199-two-furthest-houses-with-different-colors
2245-destroying-asteroids
2265-partition-array-according-to-given-pivot
2306-create-binary-tree-from-descriptions
2554-minimum-total-distance-traveled
2598-shortest-distance-to-target-string-in-a-circular-array
2634-minimum-common-value
2639-separate-the-digits-in-an-array
2708-find-the-string-with-lcp
2714-left-and-right-sum-differences
2846-robot-collisions
2855-maximum-number-of-jumps-to-reach-the-last-index
2892-check-if-array-is-good
3031-construct-product-matrix
3194-find-words-containing-character
3215-matrix-similarity-after-cyclic-shifts
3227-find-missing-and-repeated-values
3299-find-the-maximum-number-of-elements-in-subset
3329-find-the-length-of-the-longest-common-prefix
3331-minimum-operations-to-exceed-threshold-value-i
3470-maximum-score-from-grid-operations
3492-count-submatrices-with-equal-frequency-of-x-and-y
3651-transformed-array
3723-sum-of-good-numbers
3750-closest-equal-element-queries
3842-number-of-ways-to-assign-edge-weights-ii
3849-equal-sum-grid-partition-i
3933-minimum-jumps-to-reach-end-via-prime-teleportation
3958-minimum-removals-to-balance-array
3965-earliest-finish-time-for-land-and-water-rides-i
3967-earliest-finish-time-for-land-and-water-rides-ii
3974-xor-after-range-multiplication-queries-i
3975-xor-after-range-multiplication-queries-ii
3981-jump-game-ix
3986-maximum-path-score-in-a-grid
4007-maximum-total-subarray-value-ii
4074-count-subarrays-with-majority-element-i
4075-count-subarrays-with-majority-element-ii
4115-minimum-distance-between-three-equal-elements-i
4119-minimum-distance-between-three-equal-elements-ii
4139-minimum-absolute-distance-between-mirror-pairs

Sorting

0015-3sum
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
0594-longest-harmonious-subsequence
1019-squares-of-a-sorted-array
1306-minimum-absolute-difference
1466-jump-game-v
1482-how-many-numbers-are-smaller-than-the-current-number
1845-largest-submatrix-with-rearrangements
1956-maximum-element-after-decreasing-and-rearranging
1961-maximum-ice-cream-bars
1968-maximum-building-height
2245-destroying-asteroids
2554-minimum-total-distance-traveled
2846-robot-collisions
2892-check-if-array-is-good
3958-minimum-removals-to-balance-array
3965-earliest-finish-time-for-land-and-water-rides-i
3967-earliest-finish-time-for-land-and-water-rides-ii

Hash Table

0001-two-sum
0003-longest-substring-without-repeating-characters
0049-group-anagrams
0073-set-matrix-zeroes
0076-minimum-window-substring
0128-longest-consecutive-sequence
0141-linked-list-cycle
0146-lru-cache
0169-majority-element
0187-repeated-dna-sequences
0202-happy-number
0217-contains-duplicate
0219-contains-duplicate-ii
0229-majority-element-ii
0242-valid-anagram
0424-longest-repeating-character-replacement
0448-find-all-numbers-disappeared-in-an-array
0594-longest-harmonious-subsequence
0906-walking-robot-simulation
1297-maximum-number-of-balloons
1392-find-the-difference-of-two-arrays
1447-jump-game-iv
1460-number-of-substrings-containing-all-three-characters
1482-how-many-numbers-are-smaller-than-the-current-number
1793-minimum-moves-to-make-array-complementary
1987-substrings-of-size-three-with-distinct-characters
2306-create-binary-tree-from-descriptions
2634-minimum-common-value
2892-check-if-array-is-good
3227-find-missing-and-repeated-values
3299-find-the-maximum-number-of-elements-in-subset
3329-find-the-length-of-the-longest-common-prefix
3405-count-the-number-of-special-characters-ii
3408-count-the-number-of-special-characters-i
3750-closest-equal-element-queries
3933-minimum-jumps-to-reach-end-via-prime-teleportation
4055-longest-balanced-substring-i
4074-count-subarrays-with-majority-element-i
4075-count-subarrays-with-majority-element-ii
4115-minimum-distance-between-three-equal-elements-i
4119-minimum-distance-between-three-equal-elements-ii
4139-minimum-absolute-distance-between-mirror-pairs

String

0003-longest-substring-without-repeating-characters
0005-longest-palindromic-substring
0014-longest-common-prefix
0020-valid-parentheses
0049-group-anagrams
0058-length-of-last-word
0067-add-binary
0076-minimum-window-substring
0079-word-search
0125-valid-palindrome
0187-repeated-dna-sequences
0242-valid-anagram
0392-is-subsequence
0424-longest-repeating-character-replacement
0647-palindromic-substrings
0742-to-lower-case
0800-letter-case-permutation
1274-number-of-days-between-two-dates
1297-maximum-number-of-balloons
1443-minimum-distance-to-type-a-word-using-two-fingers
1460-number-of-substrings-containing-all-three-characters
1910-check-if-binary-string-has-at-most-one-segment-of-ones
1987-substrings-of-size-three-with-distinct-characters
2001-jump-game-vii
2017-minimum-number-of-flips-to-make-the-binary-string-alternating
2099-number-of-strings-that-appear-as-substrings-in-word
2137-final-value-of-variable-after-performing-operations
2197-decode-the-slanted-ciphertext
2598-shortest-distance-to-target-string-in-a-circular-array
2708-find-the-string-with-lcp
2999-check-if-strings-can-be-made-equal-with-operations-i
3019-furthest-point-from-origin
3194-find-words-containing-character
3329-find-the-length-of-the-longest-common-prefix
3405-count-the-number-of-special-characters-ii
3408-count-the-number-of-special-characters-i
3770-lexicographically-smallest-generated-string
3931-process-string-with-special-operations-i
3939-process-string-with-special-operations-ii
4055-longest-balanced-substring-i

Simulation

0054-spiral-matrix
0067-add-binary
0258-add-digits
0682-baseball-game
0906-walking-robot-simulation
2137-final-value-of-variable-after-performing-operations
2178-walking-robot-simulation-ii
2197-decode-the-slanted-ciphertext
2265-partition-array-according-to-given-pivot
2639-separate-the-digits-in-an-array
2846-robot-collisions
3215-matrix-similarity-after-cyclic-shifts
3651-transformed-array
3931-process-string-with-special-operations-i
3939-process-string-with-special-operations-ii
3974-xor-after-range-multiplication-queries-i

Sliding Window

0003-longest-substring-without-repeating-characters
0076-minimum-window-substring
0187-repeated-dna-sequences
0209-minimum-size-subarray-sum
0219-contains-duplicate-ii
0424-longest-repeating-character-replacement
0594-longest-harmonious-subsequence
0643-maximum-average-subarray-i
0713-subarray-product-less-than-k
1460-number-of-substrings-containing-all-three-characters
1987-substrings-of-size-three-with-distinct-characters
2001-jump-game-vii
2017-minimum-number-of-flips-to-make-the-binary-string-alternating
3958-minimum-removals-to-balance-array

Tree

0110-balanced-binary-tree
2306-create-binary-tree-from-descriptions
3842-number-of-ways-to-assign-edge-weights-ii
3844-number-of-ways-to-assign-edge-weights-i

Depth-First Search

0079-word-search
0110-balanced-binary-tree
1507-check-if-there-is-a-valid-path-in-a-grid
1663-detect-cycles-in-2d-grid
1840-minimize-hamming-distance-after-swap-operations
3842-number-of-ways-to-assign-edge-weights-ii
3844-number-of-ways-to-assign-edge-weights-i

Binary Tree

0110-balanced-binary-tree
2306-create-binary-tree-from-descriptions

Binary Search

0033-search-in-rotated-sorted-array
0074-search-a-2d-matrix
0153-find-minimum-in-rotated-sorted-array
0154-find-minimum-in-rotated-sorted-array-ii
0167-two-sum-ii-input-array-is-sorted
0209-minimum-size-subarray-sum
0287-find-the-duplicate-number
0493-reverse-pairs
0713-subarray-product-less-than-k
0745-find-smallest-letter-greater-than-target
0792-binary-search
1984-maximum-distance-between-a-pair-of-values
2634-minimum-common-value
3750-closest-equal-element-queries
3902-maximize-spanning-tree-stability-with-upgrades
3965-earliest-finish-time-for-land-and-water-rides-i
3967-earliest-finish-time-for-land-and-water-rides-ii

Dynamic Programming

0005-longest-palindromic-substring
0045-jump-game-ii
0053-maximum-subarray
0070-climbing-stairs
0118-pascals-triangle
0121-best-time-to-buy-and-sell-stock
0152-maximum-product-subarray
0338-counting-bits
0392-is-subsequence
0396-rotate-function
0647-palindromic-substrings
0804-rotated-digits
0815-champagne-tower
0875-longest-mountain-in-array
1443-minimum-distance-to-type-a-word-using-two-fingers
1466-jump-game-v
1716-maximum-non-negative-product-in-a-matrix
2001-jump-game-vii
2017-minimum-number-of-flips-to-make-the-binary-string-alternating
2554-minimum-total-distance-traveled
2708-find-the-string-with-lcp
2855-maximum-number-of-jumps-to-reach-the-last-index
3470-maximum-score-from-grid-operations
3842-number-of-ways-to-assign-edge-weights-ii
3962-number-of-zigzag-arrays-i
3981-jump-game-ix
3986-maximum-path-score-in-a-grid
4057-total-waviness-of-numbers-in-range-i

Greedy

0011-container-with-most-water
0045-jump-game-ii
1845-largest-submatrix-with-rearrangements
1956-maximum-element-after-decreasing-and-rearranging
1961-maximum-ice-cream-bars
2199-two-furthest-houses-with-different-colors
2245-destroying-asteroids
2708-find-the-string-with-lcp
3770-lexicographically-smallest-generated-string
3902-maximize-spanning-tree-stability-with-upgrades
3965-earliest-finish-time-for-land-and-water-rides-i
3967-earliest-finish-time-for-land-and-water-rides-ii
4007-maximum-total-subarray-value-ii

Math

0007-reverse-integer
0009-palindrome-number
0048-rotate-image
0050-powx-n
0067-add-binary
0070-climbing-stairs
0189-rotate-array
0202-happy-number
0204-count-primes
0258-add-digits
0371-sum-of-two-integers
0396-rotate-function
0804-rotated-digits
1274-number-of-days-between-two-dates
1395-minimum-time-visiting-all-points
1446-angle-between-hands-of-a-clock
1728-fancy-sequence
1968-maximum-building-height
2608-count-the-digits-that-divide-a-number
3215-matrix-similarity-after-cyclic-shifts
3227-find-missing-and-repeated-values
3842-number-of-ways-to-assign-edge-weights-ii
3844-number-of-ways-to-assign-edge-weights-i
3933-minimum-jumps-to-reach-end-via-prime-teleportation
4057-total-waviness-of-numbers-in-range-i
4139-minimum-absolute-distance-between-mirror-pairs
4168-mirror-distance-of-an-integer

Two Pointers

0005-longest-palindromic-substring
0011-container-with-most-water
0015-3sum
0019-remove-nth-node-from-end-of-list
0031-next-permutation
0075-sort-colors
0088-merge-sorted-array
0125-valid-palindrome
0141-linked-list-cycle
0143-reorder-list
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
0392-is-subsequence
0647-palindromic-substrings
0875-longest-mountain-in-array
0908-middle-of-the-linked-list
1019-squares-of-a-sorted-array
1972-rotating-the-box
1984-maximum-distance-between-a-pair-of-values
2216-delete-the-middle-node-of-a-linked-list
2236-maximum-twin-sum-of-a-linked-list
2265-partition-array-according-to-given-pivot
2634-minimum-common-value
3965-earliest-finish-time-for-land-and-water-rides-i
3967-earliest-finish-time-for-land-and-water-rides-ii

Divide and Conquer

0023-merge-k-sorted-lists
0053-maximum-subarray
0169-majority-element
0190-reverse-bits
0191-number-of-1-bits
0493-reverse-pairs
3974-xor-after-range-multiplication-queries-i
3975-xor-after-range-multiplication-queries-ii
4074-count-subarrays-with-majority-element-i
4075-count-subarrays-with-majority-element-ii

Bit Manipulation

0067-add-binary
0078-subsets
0090-subsets-ii
0136-single-number
0187-repeated-dna-sequences
0190-reverse-bits
0191-number-of-1-bits
0287-find-the-duplicate-number
0338-counting-bits
0371-sum-of-two-integers
0401-binary-watch
0693-binary-number-with-alternating-bits
0800-letter-case-permutation
3842-number-of-ways-to-assign-edge-weights-ii

Counting

0169-majority-element
0229-majority-element-ii
0594-longest-harmonious-subsequence
1297-maximum-number-of-balloons
1987-substrings-of-size-three-with-distinct-characters
3019-furthest-point-from-origin
4055-longest-balanced-substring-i
4074-count-subarrays-with-majority-element-i

Enumeration

0204-count-primes
0875-longest-mountain-in-array
3299-find-the-maximum-number-of-elements-in-subset
3849-equal-sum-grid-partition-i
4055-longest-balanced-substring-i
4057-total-waviness-of-numbers-in-range-i

Backtracking

0039-combination-sum
0040-combination-sum-ii
0046-permutations
0077-combinations
0078-subsets
0079-word-search
0090-subsets-ii
0401-binary-watch
0800-letter-case-permutation

Linked List

0019-remove-nth-node-from-end-of-list
0021-merge-two-sorted-lists
0023-merge-k-sorted-lists
0083-remove-duplicates-from-sorted-list
0141-linked-list-cycle
0143-reorder-list
0146-lru-cache
0206-reverse-linked-list
0234-palindrome-linked-list
0328-odd-even-linked-list
0908-middle-of-the-linked-list
2216-delete-the-middle-node-of-a-linked-list
2236-maximum-twin-sum-of-a-linked-list

Recursion

0021-merge-two-sorted-lists
0050-powx-n
0143-reorder-list
0206-reverse-linked-list
0234-palindrome-linked-list

Stack

0020-valid-parentheses
0143-reorder-list
0234-palindrome-linked-list
0682-baseball-game
2236-maximum-twin-sum-of-a-linked-list
2846-robot-collisions

Prefix Sum

0209-minimum-size-subarray-sum
0238-product-of-array-except-self
0303-range-sum-query-immutable
0713-subarray-product-less-than-k
1793-minimum-moves-to-make-array-complementary
2001-jump-game-vii
2714-left-and-right-sum-differences
3031-construct-product-matrix
3470-maximum-score-from-grid-operations
3492-count-submatrices-with-equal-frequency-of-x-and-y
3849-equal-sum-grid-partition-i
3962-number-of-zigzag-arrays-i
4074-count-subarrays-with-majority-element-i
4075-count-subarrays-with-majority-element-ii

Union-Find

0128-longest-consecutive-sequence
1507-check-if-there-is-a-valid-path-in-a-grid
1663-detect-cycles-in-2d-grid
1840-minimize-hamming-distance-after-swap-operations
2708-find-the-string-with-lcp
3902-maximize-spanning-tree-stability-with-upgrades

Graph Theory

3902-maximize-spanning-tree-stability-with-upgrades

Minimum Spanning Tree

3902-maximize-spanning-tree-stability-with-upgrades

Matrix

0048-rotate-image
0054-spiral-matrix
0073-set-matrix-zeroes
0074-search-a-2d-matrix
0079-word-search
1036-rotting-oranges
1507-check-if-there-is-a-valid-path-in-a-grid
1663-detect-cycles-in-2d-grid
1716-maximum-non-negative-product-in-a-matrix
1845-largest-submatrix-with-rearrangements
1972-rotating-the-box
2708-find-the-string-with-lcp
3031-construct-product-matrix
3215-matrix-similarity-after-cyclic-shifts
3227-find-missing-and-repeated-values
3470-maximum-score-from-grid-operations
3492-count-submatrices-with-equal-frequency-of-x-and-y
3849-equal-sum-grid-partition-i
3986-maximum-path-score-in-a-grid

Design

0146-lru-cache
0303-range-sum-query-immutable
1728-fancy-sequence
2178-walking-robot-simulation-ii

Segment Tree

0493-reverse-pairs
1728-fancy-sequence
4007-maximum-total-subarray-value-ii
4074-count-subarrays-with-majority-element-i
4075-count-subarrays-with-majority-element-ii

Doubly-Linked List

0146-lru-cache

Heap (Priority Queue)

0023-merge-k-sorted-lists
4007-maximum-total-subarray-value-ii

Merge Sort

0023-merge-k-sorted-lists
0493-reverse-pairs
4074-count-subarrays-with-majority-element-i
4075-count-subarrays-with-majority-element-ii

String Matching

3770-lexicographically-smallest-generated-string

Binary Indexed Tree

0493-reverse-pairs

Ordered Set

0493-reverse-pairs

Number Theory

0204-count-primes
0258-add-digits
3933-minimum-jumps-to-reach-end-via-prime-teleportation

Counting Sort

1482-how-many-numbers-are-smaller-than-the-current-number
1961-maximum-ice-cream-bars

Geometry

1395-minimum-time-visiting-all-points

Breadth-First Search

1036-rotting-oranges
1447-jump-game-iv
1507-check-if-there-is-a-valid-path-in-a-grid
1663-detect-cycles-in-2d-grid
3933-minimum-jumps-to-reach-end-via-prime-teleportation

Memoization

0070-climbing-stairs

Trie

0014-longest-common-prefix
3329-find-the-length-of-the-longest-common-prefix

Rolling Hash

0187-repeated-dna-sequences

Hash Function

0187-repeated-dna-sequences