A collection of LeetCode problems I solved to practice DSA.

LeetCode Topics

Array

0001-two-sum
0011-container-with-most-water
0026-remove-duplicates-from-sorted-array
0027-remove-element
0036-valid-sudoku
0039-combination-sum
0048-rotate-image
0049-group-anagrams
0053-maximum-subarray
0074-search-a-2d-matrix
0078-subsets
0080-remove-duplicates-from-sorted-array-ii
0090-subsets-ii
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0106-construct-binary-tree-from-inorder-and-postorder-traversal
0108-convert-sorted-array-to-binary-search-tree
0121-best-time-to-buy-and-sell-stock
0136-single-number
0139-word-break
0150-evaluate-reverse-polish-notation
0152-maximum-product-subarray
0167-two-sum-ii-input-array-is-sorted
0200-number-of-islands
0209-minimum-size-subarray-sum
0215-kth-largest-element-in-an-array
0217-contains-duplicate
0238-product-of-array-except-self
0240-search-a-2d-matrix-ii
0268-missing-number
0300-longest-increasing-subsequence
0303-range-sum-query-immutable
0304-range-sum-query-2d-immutable
0347-top-k-frequent-elements
0560-subarray-sum-equals-k
0695-max-area-of-island
0697-degree-of-an-array
0724-find-pivot-index
0792-binary-search
0817-design-hashmap
0907-koko-eating-bananas
0948-sort-an-array
1008-construct-binary-search-tree-from-preorder-traversal
1014-k-closest-points-to-origin
1036-rotting-oranges
1127-last-stone-weight
1171-shortest-path-in-binary-matrix
1256-rank-transform-of-an-array
1582-design-browser-history
1802-number-of-students-unable-to-eat-lunch
1929-concatenation-of-array
2058-concatenation-of-array
2350-find-closest-number-to-zero

Two Pointers

0011-container-with-most-water
0026-remove-duplicates-from-sorted-array
0027-remove-element
0080-remove-duplicates-from-sorted-array-ii
0125-valid-palindrome
0167-two-sum-ii-input-array-is-sorted
0344-reverse-string
1768-merge-strings-alternately
1894-merge-strings-alternately

Hash Table

0001-two-sum
0003-longest-substring-without-repeating-characters
0013-roman-to-integer
0036-valid-sudoku
0049-group-anagrams
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0106-construct-binary-tree-from-inorder-and-postorder-traversal
0133-clone-graph
0139-word-break
0146-lru-cache
0217-contains-duplicate
0242-valid-anagram
0268-missing-number
0347-top-k-frequent-elements
0424-longest-repeating-character-replacement
0560-subarray-sum-equals-k
0697-degree-of-an-array
0817-design-hashmap
1256-rank-transform-of-an-array
2427-first-letter-to-appear-twice

Sorting

0049-group-anagrams
0215-kth-largest-element-in-an-array
0217-contains-duplicate
0242-valid-anagram
0268-missing-number
0347-top-k-frequent-elements
0948-sort-an-array
1014-k-closest-points-to-origin
1256-rank-transform-of-an-array

Simulation

1802-number-of-students-unable-to-eat-lunch
1929-concatenation-of-array
2058-concatenation-of-array

String

0003-longest-substring-without-repeating-characters
0013-roman-to-integer
0020-valid-parentheses
0049-group-anagrams
0091-decode-ways
0097-interleaving-string
0125-valid-palindrome
0131-palindrome-partitioning
0139-word-break
0242-valid-anagram
0257-binary-tree-paths
0297-serialize-and-deserialize-binary-tree
0344-reverse-string
0424-longest-repeating-character-replacement
0516-longest-palindromic-subsequence
1768-merge-strings-alternately
1894-merge-strings-alternately
1967-longest-substring-of-all-vowels-in-order
2088-minimum-time-to-type-word-using-special-typewriter
2427-first-letter-to-appear-twice
3312-number-of-changing-keys

Stack

0020-valid-parentheses
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
0225-implement-stack-using-queues
0589-n-ary-tree-preorder-traversal
0590-n-ary-tree-postorder-traversal
1008-construct-binary-search-tree-from-preorder-traversal
1582-design-browser-history
1802-number-of-students-unable-to-eat-lunch

Design

0146-lru-cache
0155-min-stack
0225-implement-stack-using-queues
0297-serialize-and-deserialize-binary-tree
0303-range-sum-query-immutable
0304-range-sum-query-2d-immutable
0789-kth-largest-element-in-a-stream
0817-design-hashmap
0838-design-linked-list
1582-design-browser-history

Divide and Conquer

0053-maximum-subarray
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0106-construct-binary-tree-from-inorder-and-postorder-traversal
0108-convert-sorted-array-to-binary-search-tree
0109-convert-sorted-list-to-binary-search-tree
0190-reverse-bits
0191-number-of-1-bits
0215-kth-largest-element-in-an-array
0240-search-a-2d-matrix-ii
0347-top-k-frequent-elements
0948-sort-an-array
1014-k-closest-points-to-origin

Heap (Priority Queue)

0215-kth-largest-element-in-an-array
0347-top-k-frequent-elements
0789-kth-largest-element-in-a-stream
0948-sort-an-array
1014-k-closest-points-to-origin
1127-last-stone-weight

Bucket Sort

0347-top-k-frequent-elements
0948-sort-an-array

Counting

0347-top-k-frequent-elements
2427-first-letter-to-appear-twice

Quickselect

0215-kth-largest-element-in-an-array
0347-top-k-frequent-elements
1014-k-closest-points-to-origin

Math

0013-roman-to-integer
0048-rotate-image
0096-unique-binary-search-trees
0150-evaluate-reverse-polish-notation
0268-missing-number
0795-k-th-symbol-in-grammar
1013-fibonacci-number
1014-k-closest-points-to-origin
1137-n-th-tribonacci-number
2571-find-the-pivot-integer

Linked List

0021-merge-two-sorted-lists
0109-convert-sorted-list-to-binary-search-tree
0114-flatten-binary-tree-to-linked-list
0116-populating-next-right-pointers-in-each-node
0146-lru-cache
0206-reverse-linked-list
0817-design-hashmap
0838-design-linked-list
1582-design-browser-history

Prefix Sum

0209-minimum-size-subarray-sum
0238-product-of-array-except-self
0303-range-sum-query-immutable
0304-range-sum-query-2d-immutable
0560-subarray-sum-equals-k
0724-find-pivot-index
2571-find-the-pivot-integer

Matrix

0036-valid-sudoku
0048-rotate-image
0074-search-a-2d-matrix
0200-number-of-islands
0240-search-a-2d-matrix-ii
0304-range-sum-query-2d-immutable
0695-max-area-of-island
1036-rotting-oranges
1171-shortest-path-in-binary-matrix

Recursion

0021-merge-two-sorted-lists
0206-reverse-linked-list
0795-k-th-symbol-in-grammar
0894-all-possible-full-binary-trees
1013-fibonacci-number

Doubly-Linked List

0146-lru-cache
1582-design-browser-history

Data Stream

0789-kth-largest-element-in-a-stream
1582-design-browser-history

Queue

0225-implement-stack-using-queues
1802-number-of-students-unable-to-eat-lunch

Dynamic Programming

0053-maximum-subarray
0091-decode-ways
0095-unique-binary-search-trees-ii
0096-unique-binary-search-trees
0097-interleaving-string
0121-best-time-to-buy-and-sell-stock
0131-palindrome-partitioning
0139-word-break
0152-maximum-product-subarray
0300-longest-increasing-subsequence
0338-counting-bits
0516-longest-palindromic-subsequence
0894-all-possible-full-binary-trees
1013-fibonacci-number
1137-n-th-tribonacci-number

Memoization

0139-word-break
0894-all-possible-full-binary-trees
1013-fibonacci-number
1137-n-th-tribonacci-number

Tree

0094-binary-tree-inorder-traversal
0095-unique-binary-search-trees-ii
0096-unique-binary-search-trees
0098-validate-binary-search-tree
0100-same-tree
0101-symmetric-tree
0102-binary-tree-level-order-traversal
0103-binary-tree-zigzag-level-order-traversal
0104-maximum-depth-of-binary-tree
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0106-construct-binary-tree-from-inorder-and-postorder-traversal
0108-convert-sorted-array-to-binary-search-tree
0109-convert-sorted-list-to-binary-search-tree
0110-balanced-binary-tree
0111-minimum-depth-of-binary-tree
0112-path-sum
0113-path-sum-ii
0114-flatten-binary-tree-to-linked-list
0116-populating-next-right-pointers-in-each-node
0144-binary-tree-preorder-traversal
0145-binary-tree-postorder-traversal
0199-binary-tree-right-side-view
0226-invert-binary-tree
0230-kth-smallest-element-in-a-bst
0235-lowest-common-ancestor-of-a-binary-search-tree
0236-lowest-common-ancestor-of-a-binary-tree
0257-binary-tree-paths
0297-serialize-and-deserialize-binary-tree
0429-n-ary-tree-level-order-traversal
0450-delete-node-in-a-bst
0501-find-mode-in-binary-search-tree
0513-find-bottom-left-tree-value
0559-maximum-depth-of-n-ary-tree
0589-n-ary-tree-preorder-traversal
0590-n-ary-tree-postorder-traversal
0662-maximum-width-of-binary-tree
0701-insert-into-a-binary-search-tree
0783-search-in-a-binary-search-tree
0784-insert-into-a-binary-search-tree
0789-kth-largest-element-in-a-stream
0894-all-possible-full-binary-trees
1008-construct-binary-search-tree-from-preorder-traversal
1302-deepest-leaves-sum
2384-root-equals-sum-of-children

Depth-First Search

0094-binary-tree-inorder-traversal
0098-validate-binary-search-tree
0100-same-tree
0101-symmetric-tree
0104-maximum-depth-of-binary-tree
0110-balanced-binary-tree
0111-minimum-depth-of-binary-tree
0112-path-sum
0113-path-sum-ii
0114-flatten-binary-tree-to-linked-list
0116-populating-next-right-pointers-in-each-node
0133-clone-graph
0144-binary-tree-preorder-traversal
0145-binary-tree-postorder-traversal
0199-binary-tree-right-side-view
0200-number-of-islands
0207-course-schedule
0226-invert-binary-tree
0230-kth-smallest-element-in-a-bst
0235-lowest-common-ancestor-of-a-binary-search-tree
0236-lowest-common-ancestor-of-a-binary-tree
0257-binary-tree-paths
0297-serialize-and-deserialize-binary-tree
0501-find-mode-in-binary-search-tree
0513-find-bottom-left-tree-value
0559-maximum-depth-of-n-ary-tree
0589-n-ary-tree-preorder-traversal
0590-n-ary-tree-postorder-traversal
0662-maximum-width-of-binary-tree
0695-max-area-of-island
1302-deepest-leaves-sum

Breadth-First Search

0100-same-tree
0101-symmetric-tree
0102-binary-tree-level-order-traversal
0103-binary-tree-zigzag-level-order-traversal
0104-maximum-depth-of-binary-tree
0111-minimum-depth-of-binary-tree
0112-path-sum
0116-populating-next-right-pointers-in-each-node
0133-clone-graph
0199-binary-tree-right-side-view
0200-number-of-islands
0207-course-schedule
0226-invert-binary-tree
0297-serialize-and-deserialize-binary-tree
0429-n-ary-tree-level-order-traversal
0513-find-bottom-left-tree-value
0559-maximum-depth-of-n-ary-tree
0662-maximum-width-of-binary-tree
0695-max-area-of-island
1036-rotting-oranges
1171-shortest-path-in-binary-matrix
1302-deepest-leaves-sum

Binary Tree

0094-binary-tree-inorder-traversal
0095-unique-binary-search-trees-ii
0096-unique-binary-search-trees
0098-validate-binary-search-tree
0100-same-tree
0101-symmetric-tree
0102-binary-tree-level-order-traversal
0103-binary-tree-zigzag-level-order-traversal
0104-maximum-depth-of-binary-tree
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0106-construct-binary-tree-from-inorder-and-postorder-traversal
0108-convert-sorted-array-to-binary-search-tree
0109-convert-sorted-list-to-binary-search-tree
0110-balanced-binary-tree
0111-minimum-depth-of-binary-tree
0112-path-sum
0113-path-sum-ii
0114-flatten-binary-tree-to-linked-list
0116-populating-next-right-pointers-in-each-node
0144-binary-tree-preorder-traversal
0145-binary-tree-postorder-traversal
0199-binary-tree-right-side-view
0226-invert-binary-tree
0230-kth-smallest-element-in-a-bst
0235-lowest-common-ancestor-of-a-binary-search-tree
0236-lowest-common-ancestor-of-a-binary-tree
0257-binary-tree-paths
0297-serialize-and-deserialize-binary-tree
0450-delete-node-in-a-bst
0501-find-mode-in-binary-search-tree
0513-find-bottom-left-tree-value
0662-maximum-width-of-binary-tree
0701-insert-into-a-binary-search-tree
0783-search-in-a-binary-search-tree
0784-insert-into-a-binary-search-tree
0789-kth-largest-element-in-a-stream
0894-all-possible-full-binary-trees
1008-construct-binary-search-tree-from-preorder-traversal
1302-deepest-leaves-sum
2384-root-equals-sum-of-children

Merge Sort

0948-sort-an-array

Radix Sort

0948-sort-an-array

Counting Sort

0948-sort-an-array

Bit Manipulation

0078-subsets
0090-subsets-ii
0136-single-number
0190-reverse-bits
0191-number-of-1-bits
0268-missing-number
0338-counting-bits
0795-k-th-symbol-in-grammar
2427-first-letter-to-appear-twice

Backtracking

0039-combination-sum
0078-subsets
0090-subsets-ii
0095-unique-binary-search-trees-ii
0113-path-sum-ii
0131-palindrome-partitioning
0257-binary-tree-paths

Binary Search

0074-search-a-2d-matrix
0167-two-sum-ii-input-array-is-sorted
0209-minimum-size-subarray-sum
0240-search-a-2d-matrix-ii
0268-missing-number
0278-first-bad-version
0300-longest-increasing-subsequence
0374-guess-number-higher-or-lower
0792-binary-search
0907-koko-eating-bananas

Interactive

0278-first-bad-version
0374-guess-number-higher-or-lower

Binary Search Tree

0095-unique-binary-search-trees-ii
0096-unique-binary-search-trees
0098-validate-binary-search-tree
0108-convert-sorted-array-to-binary-search-tree
0109-convert-sorted-list-to-binary-search-tree
0230-kth-smallest-element-in-a-bst
0235-lowest-common-ancestor-of-a-binary-search-tree
0450-delete-node-in-a-bst
0501-find-mode-in-binary-search-tree
0701-insert-into-a-binary-search-tree
0783-search-in-a-binary-search-tree
0784-insert-into-a-binary-search-tree
0789-kth-largest-element-in-a-stream
1008-construct-binary-search-tree-from-preorder-traversal

Geometry

1014-k-closest-points-to-origin

Hash Function

0817-design-hashmap

Union Find

0200-number-of-islands
0695-max-area-of-island

Graph

0133-clone-graph
0207-course-schedule

Topological Sort

0207-course-schedule

Sliding Window

0003-longest-substring-without-repeating-characters
0209-minimum-size-subarray-sum
0424-longest-repeating-character-replacement
1967-longest-substring-of-all-vowels-in-order

Greedy

0011-container-with-most-water
2088-minimum-time-to-type-word-using-special-typewriter

Trie

0139-word-break

Monotonic Stack

1008-construct-binary-search-tree-from-preorder-traversal