Topics.md

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## Array
- [Two Sum](./0001.two-sum)
- [Container With Most Water](./0011.container-with-most-water)
- [3Sum](./0015.3sum)
- [3Sum Closest](./0016.3sum-closest)
- [Remove Duplicates from Sorted Array](./0026.remove-duplicates-from-sorted-array)
- [Remove Element](./0027.remove-element)
- [Next Permutation](./0031.next-permutation)
- [Search in Rotated Sorted Array](./0033.search-in-rotated-sorted-array)
- [Find First and Last Position of Element in Sorted Array](./0034.find-first-and-last-position-of-element-in-sorted-array)
- [Search Insert Position](./0035.search-insert-position)
- [First Missing Positive](./0041.first-missing-positive)
- [Trapping Rain Water](./0042.trapping-rain-water)
- [Rotate Image](./0048.rotate-image)
- [Maximum Subarray](./0053.maximum-subarray)
- [Spiral Matrix](./0054.spiral-matrix)
- [Merge Intervals](./0056.merge-intervals)
- [Insert Interval](./0057.insert-interval)
- [Spiral Matrix II](./0059.spiral-matrix-ii)
- [Unique Paths](./0062.unique-paths)
- [Unique Paths II](./0063.unique-paths-ii)
- [Minimum Path Sum](./0064.minimum-path-sum)
- [Plus One](./0066.plus-one)
- [Set Matrix Zeroes](./0073.set-matrix-zeroes)
- [Search a 2D Matrix](./0074.search-a-2d-matrix)
- [Sort Colors](./0075.sort-colors)
- [Subsets](./0078.subsets)
- [Word Search](./0079.word-search)
- [Remove Duplicates from Sorted Array II](./0080.remove-duplicates-from-sorted-array-ii)
- [Maximal Rectangle](./0085.maximal-rectangle)
- [Merge Sorted Array](./0088.merge-sorted-array)
- [Construct Binary Tree from Preorder and Inorder Traversal](./0105.construct-binary-tree-from-preorder-and-inorder-traversal)
- [Construct Binary Tree from Inorder and Postorder Traversal](./0106.construct-binary-tree-from-inorder-and-postorder-traversal)
- [Pascal's Triangle](./0118.pascals-triangle)
- [Pascal's Triangle II](./0119.pascals-triangle-ii)
- [Triangle](./0120.triangle)
- [Best Time to Buy and Sell Stock](./0121.best-time-to-buy-and-sell-stock)
- [Best Time to Buy and Sell Stock II](./0122.best-time-to-buy-and-sell-stock-ii)
- [Best Time to Buy and Sell Stock III](./0123.best-time-to-buy-and-sell-stock-iii)
- [Maximum Product Subarray](./0152.maximum-product-subarray)
- [Find Minimum in Rotated Sorted Array](./0153.find-minimum-in-rotated-sorted-array)
- [Find Minimum in Rotated Sorted Array II](./0154.find-minimum-in-rotated-sorted-array-ii)
- [Find Peak Element](./0162.find-peak-element)
- [Two Sum II - Input array is sorted](./0167.two-sum-ii-input-array-is-sorted)
- [Majority Element](./0169.majority-element)
- [Rotate Array](./0189.rotate-array)
- [Minimum Size Subarray Sum](./0209.minimum-size-subarray-sum)
- [Contains Duplicate](./0217.contains-duplicate)
- [Contains Duplicate II](./0219.contains-duplicate-ii)
- [Missing Number](./0268.missing-number)
- [Move Zeroes](./0283.move-zeroes)
- [Find the Duplicate Number](./0287.find-the-duplicate-number)
- [Find All Duplicates in an Array](./0442.find-all-duplicates-in-an-array)
- [Max Consecutive Ones](./0485.max-consecutive-ones)
- [Fibonacci Number](./0509.fibonacci-number)
- [Array Partition I](./0561.array-partition-i)
- [Valid Triangle Number](./0611.valid-triangle-number)
- [Maximum Average Subarray I](./0643.maximum-average-subarray-i)
- [Maximum Swap](./0670.maximum-swap)
- [Flipping an Image](./0832.flipping-an-image)
- [Transpose Matrix](./0867.transpose-matrix)
- [Sort Array By Parity](./0905.sort-array-by-parity)
- [Sort Array By Parity II](./0922.sort-array-by-parity-ii)
- [Reveal Cards In Increasing Order](./0950.reveal-cards-in-increasing-order)
- [Pancake Sorting](./0969.pancake-sorting)
- [Squares of a Sorted Array](./0977.squares-of-a-sorted-array)
- [Add to Array-Form of Integer](./0989.add-to-array-form-of-integer)
- [Find Common Characters](./1002.find-common-characters)
- [Height Checker](./1051.height-checker)
- [Duplicate Zeros](./1089.duplicate-zeros)
- [Compare Strings by Frequency of the Smallest Character](./1170.compare-strings-by-frequency-of-the-smallest-character)
- [Distance Between Bus Stops](./1184.distance-between-bus-stops)
- [Day of the Week](./1185.day-of-the-week)
- [Minimum Absolute Difference](./1200.minimum-absolute-difference)
- [Smallest String With Swaps](./1202.smallest-string-with-swaps)
- [Play with Chips](./1217.play-with-chips)
- [Remove Sub-Folders from the Filesystem](./1233.remove-sub-folders-from-the-filesystem)
- [Cells with Odd Values in a Matrix](./1252.cells-with-odd-values-in-a-matrix)
- [Shift 2D Grid](./1260.shift-2d-grid)
## Backtracking
- [Regular Expression Matching](./0010.regular-expression-matching)
- [Letter Combinations of a Phone Number](./0017.letter-combinations-of-a-phone-number)
- [Generate Parentheses](./0022.generate-parentheses)
- [Permutations II](./0047.permutations-ii)
- [Subsets](./0078.subsets)
- [Word Search](./0079.word-search)
- [Count Numbers with Unique Digits](./0357.count-numbers-with-unique-digits)
- [Path with Maximum Gold](./1219.path-with-maximum-gold)
- [Tiling a Rectangle with the Fewest Squares](./1240.tiling-a-rectangle-with-the-fewest-squares)
## Binary Indexed Tree
- [Count of Smaller Numbers After Self](./0315.count-of-smaller-numbers-after-self)
## Binary Search
- [Search in Rotated Sorted Array](./0033.search-in-rotated-sorted-array)
- [Find First and Last Position of Element in Sorted Array](./0034.find-first-and-last-position-of-element-in-sorted-array)
- [Search Insert Position](./0035.search-insert-position)
- [Pow(x, n)](./0050.powx-n)
- [Sqrt(x)](./0069.sqrtx)
- [Search a 2D Matrix](./0074.search-a-2d-matrix)
- [Find Minimum in Rotated Sorted Array](./0153.find-minimum-in-rotated-sorted-array)
- [Find Minimum in Rotated Sorted Array II](./0154.find-minimum-in-rotated-sorted-array-ii)
- [Find Peak Element](./0162.find-peak-element)
- [Two Sum II - Input array is sorted](./0167.two-sum-ii-input-array-is-sorted)
- [Minimum Size Subarray Sum](./0209.minimum-size-subarray-sum)
- [Count Complete Tree Nodes](./0222.count-complete-tree-nodes)
- [Kth Smallest Element in a BST](./0230.kth-smallest-element-in-a-bst)
- [Search a 2D Matrix II](./0240.search-a-2d-matrix-ii)
- [First Bad Version](./0278.first-bad-version)
- [Find the Duplicate Number](./0287.find-the-duplicate-number)
- [Longest Increasing Subsequence](./0300.longest-increasing-subsequence)
- [Count of Smaller Numbers After Self](./0315.count-of-smaller-numbers-after-self)
- [Intersection of Two Arrays](./0349.intersection-of-two-arrays)
- [Intersection of Two Arrays II](./0350.intersection-of-two-arrays-ii)
- [Guess Number Higher or Lower](./0374.guess-number-higher-or-lower)
- [Kth Smallest Element in a Sorted Matrix](./0378.kth-smallest-element-in-a-sorted-matrix)
- [Binary Search](./0704.binary-search)
- [Find Smallest Letter Greater Than Target](./0744.find-smallest-letter-greater-than-target)
- [Peak Index in a Mountain Array](./0852.peak-index-in-a-mountain-array)
- [Find Positive Integer Solution for a Given Equation](./1237.find-positive-integer-solution-for-a-given-equation)
## Binary Search Tree
- [Binary Search Tree to Greater Sum Tree](./1038.binary-search-tree-to-greater-sum-tree)
## Bit Manipulation
- [Subsets](./0078.subsets)
- [Single Number](./0136.single-number)
- [Single Number II](./0137.single-number-ii)
- [Majority Element](./0169.majority-element)
- [Number of 1 Bits](./0191.number-of-1-bits)
- [Bitwise AND of Numbers Range](./0201.bitwise-and-of-numbers-range)
- [Power of Two](./0231.power-of-two)
- [Single Number III](./0260.single-number-iii)
- [Missing Number](./0268.missing-number)
- [Counting Bits](./0338.counting-bits)
- [Power of Four](./0342.power-of-four)
- [Sum of Two Integers](./0371.sum-of-two-integers)
- [Find the Difference](./0389.find-the-difference)
- [Hamming Distance](./0461.hamming-distance)
- [Number Complement](./0476.number-complement)
- [Maximum Score Words Formed by Letters](./1255.maximum-score-words-formed-by-letters)
## Brainteaser
- [Nim Game](./0292.nim-game)
- [Bulb Switcher](./0319.bulb-switcher)
- [Airplane Seat Assignment Probability](./1227.airplane-seat-assignment-probability)
## Breadth-first Search
- [Symmetric Tree](./0101.symmetric-tree)
- [Binary Tree Level Order Traversal](./0102.binary-tree-level-order-traversal)
- [Binary Tree Zigzag Level Order Traversal](./0103.binary-tree-zigzag-level-order-traversal)
- [Binary Tree Level Order Traversal II](./0107.binary-tree-level-order-traversal-ii)
- [Minimum Depth of Binary Tree](./0111.minimum-depth-of-binary-tree)
- [Surrounded Regions](./0130.surrounded-regions)
- [Binary Tree Right Side View](./0199.binary-tree-right-side-view)
- [Number of Islands](./0200.number-of-islands)
- [Perfect Squares](./0279.perfect-squares)
- [N-ary Tree Level Order Traversal](./0429.n-ary-tree-level-order-traversal)
- [Find Bottom Left Tree Value](./0513.find-bottom-left-tree-value)
- [Find Largest Value in Each Tree Row](./0515.find-largest-value-in-each-tree-row)
- [Maximum Depth of N-ary Tree](./0559.maximum-depth-of-n-ary-tree)
- [Cousins in Binary Tree](./0993.cousins-in-binary-tree)
## Depth-first Search
- [Validate Binary Search Tree](./0098.validate-binary-search-tree)
- [Recover Binary Search Tree](./0099.recover-binary-search-tree)
- [Same Tree](./0100.same-tree)
- [Symmetric Tree](./0101.symmetric-tree)
- [Maximum Depth of Binary Tree](./0104.maximum-depth-of-binary-tree)
- [Construct Binary Tree from Preorder and Inorder Traversal](./0105.construct-binary-tree-from-preorder-and-inorder-traversal)
- [Construct Binary Tree from Inorder and Postorder Traversal](./0106.construct-binary-tree-from-inorder-and-postorder-traversal)
- [Convert Sorted Array to Binary Search Tree](./0108.convert-sorted-array-to-binary-search-tree)
- [Convert Sorted List to Binary Search Tree](./0109.convert-sorted-list-to-binary-search-tree)
- [Balanced Binary Tree](./0110.balanced-binary-tree)
- [Minimum Depth of Binary Tree](./0111.minimum-depth-of-binary-tree)
- [Path Sum](./0112.path-sum)
- [Path Sum II](./0113.path-sum-ii)
- [Flatten Binary Tree to Linked List](./0114.flatten-binary-tree-to-linked-list)
- [Populating Next Right Pointers in Each Node](./0116.populating-next-right-pointers-in-each-node)
- [Populating Next Right Pointers in Each Node II](./0117.populating-next-right-pointers-in-each-node-ii)
- [Binary Tree Maximum Path Sum](./0124.binary-tree-maximum-path-sum)
- [Sum Root to Leaf Numbers](./0129.sum-root-to-leaf-numbers)
- [Surrounded Regions](./0130.surrounded-regions)
- [Binary Tree Right Side View](./0199.binary-tree-right-side-view)
- [Number of Islands](./0200.number-of-islands)
- [Binary Tree Paths](./0257.binary-tree-paths)
- [Longest Increasing Path in a Matrix](./0329.longest-increasing-path-in-a-matrix)
- [House Robber III](./0337.house-robber-iii)
- [Flatten a Multilevel Doubly Linked List](./0430.flatten-a-multilevel-doubly-linked-list)
- [Find Bottom Left Tree Value](./0513.find-bottom-left-tree-value)
- [Find Largest Value in Each Tree Row](./0515.find-largest-value-in-each-tree-row)
- [Maximum Depth of N-ary Tree](./0559.maximum-depth-of-n-ary-tree)
- [Keys and Rooms](./0841.keys-and-rooms)
- [Leaf-Similar Trees](./0872.leaf-similar-trees)
- [Increasing Order Search Tree](./0897.increasing-order-search-tree)
- [Binary Tree Cameras](./0968.binary-tree-cameras)
- [Distribute Coins in Binary Tree](./0979.distribute-coins-in-binary-tree)
- [Smallest String Starting From Leaf](./0988.smallest-string-starting-from-leaf)
- [Maximum Difference Between Node and Ancestor](./1026.maximum-difference-between-node-and-ancestor)
- [Recover a Tree From Preorder Traversal](./1028.recover-a-tree-from-preorder-traversal)
- [Delete Nodes And Return Forest](./1110.delete-nodes-and-return-forest)
- [Lowest Common Ancestor of Deepest Leaves](./1123.lowest-common-ancestor-of-deepest-leaves)
- [Number of Closed Islands](./1254.number-of-closed-islands)
## Design
- [Min Stack](./0155.min-stack)
- [Binary Search Tree Iterator](./0173.binary-search-tree-iterator)
- [Implement Queue using Stacks](./0232.implement-queue-using-stacks)
- [Serialize and Deserialize Binary Tree](./0297.serialize-and-deserialize-binary-tree)
- [Design Linked List](./0707.design-linked-list)
## Divide and Conquer
- [Merge k Sorted Lists](./0023.merge-k-sorted-lists)
- [Maximum Subarray](./0053.maximum-subarray)
- [Majority Element](./0169.majority-element)
- [Kth Largest Element in an Array](./0215.kth-largest-element-in-an-array)
- [Search a 2D Matrix II](./0240.search-a-2d-matrix-ii)
- [Burst Balloons](./0312.burst-balloons)
- [Count of Smaller Numbers After Self](./0315.count-of-smaller-numbers-after-self)
## Dynamic Programming
- [Longest Palindromic Substring](./0005.longest-palindromic-substring)
- [Regular Expression Matching](./0010.regular-expression-matching)
- [Maximum Subarray](./0053.maximum-subarray)
- [Unique Paths](./0062.unique-paths)
- [Unique Paths II](./0063.unique-paths-ii)
- [Minimum Path Sum](./0064.minimum-path-sum)
- [Climbing Stairs](./0070.climbing-stairs)
- [Edit Distance](./0072.edit-distance)
- [Maximal Rectangle](./0085.maximal-rectangle)
- [Decode Ways](./0091.decode-ways)
- [Unique Binary Search Trees II](./0095.unique-binary-search-trees-ii)
- [Unique Binary Search Trees](./0096.unique-binary-search-trees)
- [Triangle](./0120.triangle)
- [Best Time to Buy and Sell Stock](./0121.best-time-to-buy-and-sell-stock)
- [Best Time to Buy and Sell Stock III](./0123.best-time-to-buy-and-sell-stock-iii)
- [Word Break](./0139.word-break)
- [Maximum Product Subarray](./0152.maximum-product-subarray)
- [House Robber](./0198.house-robber)
- [House Robber II](./0213.house-robber-ii)
- [Maximal Square](./0221.maximal-square)
- [Ugly Number II](./0264.ugly-number-ii)
- [Perfect Squares](./0279.perfect-squares)
- [Longest Increasing Subsequence](./0300.longest-increasing-subsequence)
- [Range Sum Query - Immutable](./0303.range-sum-query-immutable)
- [Burst Balloons](./0312.burst-balloons)
- [Coin Change](./0322.coin-change)
- [Counting Bits](./0338.counting-bits)
- [Integer Break](./0343.integer-break)
- [Count Numbers with Unique Digits](./0357.count-numbers-with-unique-digits)
- [Guess Number Higher or Lower II](./0375.guess-number-higher-or-lower-ii)
- [Continuous Subarray Sum](./0523.continuous-subarray-sum)
- [Stone Game](./0877.stone-game)
- [Minimum Falling Path Sum](./0931.minimum-falling-path-sum)
- [Binary Tree Cameras](./0968.binary-tree-cameras)
- [Divisor Game](./1025.divisor-game)
- [Last Stone Weight II](./1049.last-stone-weight-ii)
- [Minimum Cost Tree From Leaf Values](./1130.minimum-cost-tree-from-leaf-values)
- [Longest Common Subsequence](./1143.longest-common-subsequence)
- [Airplane Seat Assignment Probability](./1227.airplane-seat-assignment-probability)
- [Tiling a Rectangle with the Fewest Squares](./1240.tiling-a-rectangle-with-the-fewest-squares)
- [Greatest Sum Divisible by Three](./1262.greatest-sum-divisible-by-three)
## Graph
- [Keys and Rooms](./0841.keys-and-rooms)
- [Partition Array for Maximum Sum](./1043.partition-array-for-maximum-sum)
- [Maximum Level Sum of a Binary Tree](./1161.maximum-level-sum-of-a-binary-tree)
## Greedy
- [Best Time to Buy and Sell Stock II](./0122.best-time-to-buy-and-sell-stock-ii)
- [Partition Labels](./0763.partition-labels)
- [Walking Robot Simulation](./0874.walking-robot-simulation)
- [Minimum Add to Make Parentheses Valid](./0921.minimum-add-to-make-parentheses-valid)
- [Delete Columns to Make Sorted](./0944.delete-columns-to-make-sorted)
- [Last Stone Weight](./1046.last-stone-weight)
- [Play with Chips](./1217.play-with-chips)
- [Split a String in Balanced Strings](./1221.split-a-string-in-balanced-strings)
- [Minimum Swaps to Make Strings Equal](./1247.minimum-swaps-to-make-strings-equal)
## Hash Table
- [Two Sum](./0001.two-sum)
- [Longest Substring Without Repeating Characters](./0003.longest-substring-without-repeating-characters)
- [Group Anagrams](./0049.group-anagrams)
- [Minimum Window Substring](./0076.minimum-window-substring)
- [Maximal Rectangle](./0085.maximal-rectangle)
- [Binary Tree Inorder Traversal](./0094.binary-tree-inorder-traversal)
- [Single Number](./0136.single-number)
- [Copy List with Random Pointer](./0138.copy-list-with-random-pointer)
- [Happy Number](./0202.happy-number)
- [Count Primes](./0204.count-primes)
- [Contains Duplicate](./0217.contains-duplicate)
- [Contains Duplicate II](./0219.contains-duplicate-ii)
- [Valid Anagram](./0242.valid-anagram)
- [Word Pattern](./0290.word-pattern)
- [Intersection of Two Arrays](./0349.intersection-of-two-arrays)
- [Intersection of Two Arrays II](./0350.intersection-of-two-arrays-ii)
- [First Unique Character in a String](./0387.first-unique-character-in-a-string)
- [Find the Difference](./0389.find-the-difference)
- [Longest Palindrome](./0409.longest-palindrome)
- [Island Perimeter](./0463.island-perimeter)
- [Keyboard Row](./0500.keyboard-row)
- [Most Frequent Subtree Sum](./0508.most-frequent-subtree-sum)
- [Encode and Decode TinyURL](./0535.encode-and-decode-tinyurl)
- [Distribute Candies](./0575.distribute-candies)
- [Daily Temperatures](./0739.daily-temperatures)
- [Jewels and Stones](./0771.jewels-and-stones)
- [Rabbits in Forest](./0781.rabbits-in-forest)
- [Subdomain Visit Count](./0811.subdomain-visit-count)
- [Uncommon Words from Two Sentences](./0884.uncommon-words-from-two-sentences)
- [N-Repeated Element in Size 2N Array](./0961.n-repeated-element-in-size-2n-array)
- [Vertical Order Traversal of a Binary Tree](./0987.vertical-order-traversal-of-a-binary-tree)
- [Find Common Characters](./1002.find-common-characters)
- [Flip Columns For Maximum Number of Equal Rows](./1072.flip-columns-for-maximum-number-of-equal-rows)
- [Occurrences After Bigram](./1078.occurrences-after-bigram)
- [Maximum Number of Balloons](./1189.maximum-number-of-balloons)
- [Unique Number of Occurrences](./1207.unique-number-of-occurrences)
- [Find Elements in a Contaminated Binary Tree](./1261.find-elements-in-a-contaminated-binary-tree)
## Heap
- [Merge k Sorted Lists](./0023.merge-k-sorted-lists)
- [Kth Largest Element in an Array](./0215.kth-largest-element-in-an-array)
- [Sliding Window Maximum](./0239.sliding-window-maximum)
- [Ugly Number II](./0264.ugly-number-ii)
- [Kth Smallest Element in a Sorted Matrix](./0378.kth-smallest-element-in-a-sorted-matrix)
- [Last Stone Weight](./1046.last-stone-weight)
## Linked List
- [Add Two Numbers](./0002.add-two-numbers)
- [Remove Nth Node From End of List](./0019.remove-nth-node-from-end-of-list)
- [Merge Two Sorted Lists](./0021.merge-two-sorted-lists)
- [Merge k Sorted Lists](./0023.merge-k-sorted-lists)
- [Swap Nodes in Pairs](./0024.swap-nodes-in-pairs)
- [Reverse Nodes in k-Group](./0025.reverse-nodes-in-k-group)
- [Rotate List](./0061.rotate-list)
- [Remove Duplicates from Sorted List II](./0082.remove-duplicates-from-sorted-list-ii)
- [Remove Duplicates from Sorted List](./0083.remove-duplicates-from-sorted-list)
- [Partition List](./0086.partition-list)
- [Reverse Linked List II](./0092.reverse-linked-list-ii)
- [Convert Sorted List to Binary Search Tree](./0109.convert-sorted-list-to-binary-search-tree)
- [Copy List with Random Pointer](./0138.copy-list-with-random-pointer)
- [Linked List Cycle](./0141.linked-list-cycle)
- [Linked List Cycle II](./0142.linked-list-cycle-ii)
- [Reorder List](./0143.reorder-list)
- [Intersection of Two Linked Lists](./0160.intersection-of-two-linked-lists)
- [Remove Linked List Elements](./0203.remove-linked-list-elements)
- [Reverse Linked List](./0206.reverse-linked-list)
- [Palindrome Linked List](./0234.palindrome-linked-list)
- [Delete Node in a Linked List](./0237.delete-node-in-a-linked-list)
- [Odd Even Linked List](./0328.odd-even-linked-list)
- [Flatten a Multilevel Doubly Linked List](./0430.flatten-a-multilevel-doubly-linked-list)
- [Add Two Numbers II](./0445.add-two-numbers-ii)
- [Design Linked List](./0707.design-linked-list)
- [Split Linked List in Parts](./0725.split-linked-list-in-parts)
- [Linked List Components](./0817.linked-list-components)
- [Middle of the Linked List](./0876.middle-of-the-linked-list)
- [Next Greater Node In Linked List](./1019.next-greater-node-in-linked-list)
- [Remove Zero Sum Consecutive Nodes from Linked List](./1171.remove-zero-sum-consecutive-nodes-from-linked-list)
## Math
- [Add Two Numbers](./0002.add-two-numbers)
- [Reverse Integer](./0007.reverse-integer)
- [String to Integer (atoi)](./0008.string-to-integer-atoi)
- [Palindrome Number](./0009.palindrome-number)
- [Integer to Roman](./0012.integer-to-roman)
- [Roman to Integer](./0013.roman-to-integer)
- [Pow(x, n)](./0050.powx-n)
- [Valid Number](./0065.valid-number)
- [Add Binary](./0067.add-binary)
- [Sqrt(x)](./0069.sqrtx)
- [Excel Sheet Column Title](./0168.excel-sheet-column-title)
- [Excel Sheet Column Number](./0171.excel-sheet-column-number)
- [Happy Number](./0202.happy-number)
- [Count Primes](./0204.count-primes)
- [Power of Two](./0231.power-of-two)
- [Number of Digit One](./0233.number-of-digit-one)
- [Ugly Number](./0263.ugly-number)
- [Ugly Number II](./0264.ugly-number-ii)
- [Missing Number](./0268.missing-number)
- [Perfect Squares](./0279.perfect-squares)
- [Bulb Switcher](./0319.bulb-switcher)
- [Power of Three](./0326.power-of-three)
- [Integer Break](./0343.integer-break)
- [Count Numbers with Unique Digits](./0357.count-numbers-with-unique-digits)
- [Super Pow](./0372.super-pow)
- [Nth Digit](./0400.nth-digit)
- [Continuous Subarray Sum](./0523.continuous-subarray-sum)
- [Encode and Decode TinyURL](./0535.encode-and-decode-tinyurl)
- [Maximum Swap](./0670.maximum-swap)
- [Self Dividing Numbers](./0728.self-dividing-numbers)
- [Rabbits in Forest](./0781.rabbits-in-forest)
- [Stone Game](./0877.stone-game)
- [Smallest Range I](./0908.smallest-range-i)
- [DI String Match](./0942.di-string-match)
- [Complement of Base 10 Integer](./1009.complement-of-base-10-integer)
- [Divisor Game](./1025.divisor-game)
- [Robot Bounded In Circle](./1041.robot-bounded-in-circle)
- [Path In Zigzag Labelled Binary Tree](./1104.path-in-zigzag-labelled-binary-tree)
- [Day of the Year](./1154.day-of-the-year)
- [Play with Chips](./1217.play-with-chips)
- [Airplane Seat Assignment Probability](./1227.airplane-seat-assignment-probability)
- [Find Positive Integer Solution for a Given Equation](./1237.find-positive-integer-solution-for-a-given-equation)
- [Check If It Is a Good Array](./1250.check-if-it-is-a-good-array)
## Memoization
- [Longest Increasing Path in a Matrix](./0329.longest-increasing-path-in-a-matrix)
## Minimax
- [Nim Game](./0292.nim-game)
- [Guess Number Higher or Lower II](./0375.guess-number-higher-or-lower-ii)
- [Stone Game](./0877.stone-game)
## Ordered Map
- [Contains Duplicate III](./0220.contains-duplicate-iii)
## Queue
- [Number of Recent Calls](./0933.number-of-recent-calls)
## Random
- [Implement Rand10() Using Rand7()](./0470.implement-rand10-using-rand7)
## Recursion
- [Minimum Distance Between BST Nodes](./0783.minimum-distance-between-bst-nodes)
- [All Possible Full Binary Trees](./0894.all-possible-full-binary-trees)
- [Range Sum of BST](./0938.range-sum-of-bst)
## Rejection Sampling
- [Implement Rand10() Using Rand7()](./0470.implement-rand10-using-rand7)
## Segment Tree
- [Count of Smaller Numbers After Self](./0315.count-of-smaller-numbers-after-self)
## Sliding Window
- [Longest Substring Without Repeating Characters](./0003.longest-substring-without-repeating-characters)
- [Minimum Window Substring](./0076.minimum-window-substring)
- [Sliding Window Maximum](./0239.sliding-window-maximum)
- [Max Consecutive Ones III](./1004.max-consecutive-ones-iii)
## Sort
- [Merge Intervals](./0056.merge-intervals)
- [Insert Interval](./0057.insert-interval)
- [Sort Colors](./0075.sort-colors)
- [Largest Number](./0179.largest-number)
- [Contains Duplicate III](./0220.contains-duplicate-iii)
- [Valid Anagram](./0242.valid-anagram)
- [Count of Smaller Numbers After Self](./0315.count-of-smaller-numbers-after-self)
- [Intersection of Two Arrays](./0349.intersection-of-two-arrays)
- [Intersection of Two Arrays II](./0350.intersection-of-two-arrays-ii)
- [Sort Array By Parity II](./0922.sort-array-by-parity-ii)
- [Pancake Sorting](./0969.pancake-sorting)
## Stack
- [Valid Parentheses](./0020.valid-parentheses)
- [Trapping Rain Water](./0042.trapping-rain-water)
- [Simplify Path](./0071.simplify-path)
- [Maximal Rectangle](./0085.maximal-rectangle)
- [Binary Tree Inorder Traversal](./0094.binary-tree-inorder-traversal)
- [Binary Tree Zigzag Level Order Traversal](./0103.binary-tree-zigzag-level-order-traversal)
- [Binary Tree Preorder Traversal](./0144.binary-tree-preorder-traversal)
- [Binary Tree Postorder Traversal](./0145.binary-tree-postorder-traversal)
- [Evaluate Reverse Polish Notation](./0150.evaluate-reverse-polish-notation)
- [Min Stack](./0155.min-stack)
- [Binary Search Tree Iterator](./0173.binary-search-tree-iterator)
- [Implement Queue using Stacks](./0232.implement-queue-using-stacks)
- [Verify Preorder Serialization of a Binary Tree](./0331.verify-preorder-serialization-of-a-binary-tree)
- [Next Greater Element I](./0496.next-greater-element-i)
- [Next Greater Element II](./0503.next-greater-element-ii)
- [Daily Temperatures](./0739.daily-temperatures)
- [Minimum Add to Make Parentheses Valid](./0921.minimum-add-to-make-parentheses-valid)
- [Validate Stack Sequences](./0946.validate-stack-sequences)
- [Next Greater Node In Linked List](./1019.next-greater-node-in-linked-list)
- [Remove Outermost Parentheses](./1021.remove-outermost-parentheses)
- [Minimum Cost Tree From Leaf Values](./1130.minimum-cost-tree-from-leaf-values)
- [Reverse Substrings Between Each Pair of Parentheses](./1190.reverse-substrings-between-each-pair-of-parentheses)
- [Remove All Adjacent Duplicates in String II](./1209.remove-all-adjacent-duplicates-in-string-ii)
- [Minimum Remove to Make Valid Parentheses](./1249.minimum-remove-to-make-valid-parentheses)
## String
- [Longest Substring Without Repeating Characters](./0003.longest-substring-without-repeating-characters)
- [Longest Palindromic Substring](./0005.longest-palindromic-substring)
- [ZigZag Conversion](./0006.zigzag-conversion)
- [String to Integer (atoi)](./0008.string-to-integer-atoi)
- [Regular Expression Matching](./0010.regular-expression-matching)
- [Integer to Roman](./0012.integer-to-roman)
- [Roman to Integer](./0013.roman-to-integer)
- [Longest Common Prefix](./0014.longest-common-prefix)
- [Letter Combinations of a Phone Number](./0017.letter-combinations-of-a-phone-number)
- [Valid Parentheses](./0020.valid-parentheses)
- [Generate Parentheses](./0022.generate-parentheses)
- [Group Anagrams](./0049.group-anagrams)
- [Length of Last Word](./0058.length-of-last-word)
- [Valid Number](./0065.valid-number)
- [Add Binary](./0067.add-binary)
- [Simplify Path](./0071.simplify-path)
- [Edit Distance](./0072.edit-distance)
- [Minimum Window Substring](./0076.minimum-window-substring)
- [Decode Ways](./0091.decode-ways)
- [Valid Palindrome](./0125.valid-palindrome)
- [Reverse Words in a String](./0151.reverse-words-in-a-string)
- [Reverse String](./0344.reverse-string)
- [Reverse Vowels of a String](./0345.reverse-vowels-of-a-string)
- [Ransom Note](./0383.ransom-note)
- [First Unique Character in a String](./0387.first-unique-character-in-a-string)
- [Add Strings](./0415.add-strings)
- [Number of Segments in a String](./0434.number-of-segments-in-a-string)
- [Repeated Substring Pattern](./0459.repeated-substring-pattern)
- [Detect Capital](./0520.detect-capital)
- [Longest Uncommon Subsequence I ](./0521.longest-uncommon-subsequence-i)
- [Reverse String II](./0541.reverse-string-ii)
- [Student Attendance Record I](./0551.student-attendance-record-i)
- [Next Greater Element III](./0556.next-greater-element-iii)
- [Reverse Words in a String III](./0557.reverse-words-in-a-string-iii)
- [Delete Operation for Two Strings](./0583.delete-operation-for-two-strings)
- [Construct String from Binary Tree](./0606.construct-string-from-binary-tree)
- [Robot Return to Origin](./0657.robot-return-to-origin)
- [To Lower Case](./0709.to-lower-case)
- [Rotated Digits](./0788.rotated-digits)
- [Custom Sort String](./0791.custom-sort-string)
- [Unique Morse Code Words](./0804.unique-morse-code-words)
- [Most Common Word](./0819.most-common-word)
- [Goat Latin](./0824.goat-latin)
- [Buddy Strings](./0859.buddy-strings)
- [Reverse Only Letters](./0917.reverse-only-letters)
- [Unique Email Addresses](./0929.unique-email-addresses)
- [Greatest Common Divisor of Strings](./1071.greatest-common-divisor-of-strings)
- [Parsing A Boolean Expression](./1106.parsing-a-boolean-expression)
- [Defanging an IP Address](./1108.defanging-an-ip-address)
- [Compare Strings by Frequency of the Smallest Character](./1170.compare-strings-by-frequency-of-the-smallest-character)
- [Maximum Number of Balloons](./1189.maximum-number-of-balloons)
- [Split a String in Balanced Strings](./1221.split-a-string-in-balanced-strings)
- [Remove Sub-Folders from the Filesystem](./1233.remove-sub-folders-from-the-filesystem)
- [Minimum Swaps to Make Strings Equal](./1247.minimum-swaps-to-make-strings-equal)
- [Minimum Remove to Make Valid Parentheses](./1249.minimum-remove-to-make-valid-parentheses)
## Topological Sort
- [Longest Increasing Path in a Matrix](./0329.longest-increasing-path-in-a-matrix)
## Tree
- [Binary Tree Inorder Traversal](./0094.binary-tree-inorder-traversal)
- [Unique Binary Search Trees II](./0095.unique-binary-search-trees-ii)
- [Unique Binary Search Trees](./0096.unique-binary-search-trees)
- [Validate Binary Search Tree](./0098.validate-binary-search-tree)
- [Recover Binary Search Tree](./0099.recover-binary-search-tree)
- [Same Tree](./0100.same-tree)
- [Symmetric Tree](./0101.symmetric-tree)
- [Binary Tree Level Order Traversal](./0102.binary-tree-level-order-traversal)
- [Binary Tree Zigzag Level Order Traversal](./0103.binary-tree-zigzag-level-order-traversal)
- [Maximum Depth of Binary Tree](./0104.maximum-depth-of-binary-tree)
- [Construct Binary Tree from Preorder and Inorder Traversal](./0105.construct-binary-tree-from-preorder-and-inorder-traversal)
- [Construct Binary Tree from Inorder and Postorder Traversal](./0106.construct-binary-tree-from-inorder-and-postorder-traversal)
- [Binary Tree Level Order Traversal II](./0107.binary-tree-level-order-traversal-ii)
- [Convert Sorted Array to Binary Search Tree](./0108.convert-sorted-array-to-binary-search-tree)
- [Balanced Binary Tree](./0110.balanced-binary-tree)
- [Minimum Depth of Binary Tree](./0111.minimum-depth-of-binary-tree)
- [Path Sum](./0112.path-sum)
- [Path Sum II](./0113.path-sum-ii)
- [Flatten Binary Tree to Linked List](./0114.flatten-binary-tree-to-linked-list)
- [Populating Next Right Pointers in Each Node](./0116.populating-next-right-pointers-in-each-node)
- [Populating Next Right Pointers in Each Node II](./0117.populating-next-right-pointers-in-each-node-ii)
- [Binary Tree Maximum Path Sum](./0124.binary-tree-maximum-path-sum)
- [Sum Root to Leaf Numbers](./0129.sum-root-to-leaf-numbers)
- [Binary Tree Preorder Traversal](./0144.binary-tree-preorder-traversal)
- [Binary Tree Postorder Traversal](./0145.binary-tree-postorder-traversal)
- [Binary Search Tree Iterator](./0173.binary-search-tree-iterator)
- [Binary Tree Right Side View](./0199.binary-tree-right-side-view)
- [Count Complete Tree Nodes](./0222.count-complete-tree-nodes)
- [Invert Binary Tree](./0226.invert-binary-tree)
- [Kth Smallest Element in a BST](./0230.kth-smallest-element-in-a-bst)
- [Lowest Common Ancestor of a Binary Search Tree](./0235.lowest-common-ancestor-of-a-binary-search-tree)
- [Lowest Common Ancestor of a Binary Tree](./0236.lowest-common-ancestor-of-a-binary-tree)
- [Binary Tree Paths](./0257.binary-tree-paths)
- [Serialize and Deserialize Binary Tree](./0297.serialize-and-deserialize-binary-tree)
- [House Robber III](./0337.house-robber-iii)
- [Sum of Left Leaves](./0404.sum-of-left-leaves)
- [N-ary Tree Level Order Traversal](./0429.n-ary-tree-level-order-traversal)
- [Path Sum III](./0437.path-sum-iii)
- [Serialize and Deserialize BST](./0449.serialize-and-deserialize-bst)
- [Most Frequent Subtree Sum](./0508.most-frequent-subtree-sum)
- [Find Bottom Left Tree Value](./0513.find-bottom-left-tree-value)
- [Find Largest Value in Each Tree Row](./0515.find-largest-value-in-each-tree-row)
- [Minimum Absolute Difference in BST](./0530.minimum-absolute-difference-in-bst)
- [Convert BST to Greater Tree](./0538.convert-bst-to-greater-tree)
- [Diameter of Binary Tree](./0543.diameter-of-binary-tree)
- [Maximum Depth of N-ary Tree](./0559.maximum-depth-of-n-ary-tree)
- [N-ary Tree Preorder Traversal](./0589.n-ary-tree-preorder-traversal)
- [N-ary Tree Postorder Traversal](./0590.n-ary-tree-postorder-traversal)
- [Construct String from Binary Tree](./0606.construct-string-from-binary-tree)
- [Merge Two Binary Trees](./0617.merge-two-binary-trees)
- [Average of Levels in Binary Tree](./0637.average-of-levels-in-binary-tree)
- [Two Sum IV - Input is a BST](./0653.two-sum-iv-input-is-a-bst)
- [Maximum Binary Tree](./0654.maximum-binary-tree)
- [Print Binary Tree](./0655.print-binary-tree)
- [Maximum Width of Binary Tree](./0662.maximum-width-of-binary-tree)
- [Trim a Binary Search Tree](./0669.trim-a-binary-search-tree)
- [Second Minimum Node In a Binary Tree](./0671.second-minimum-node-in-a-binary-tree)
- [Search in a Binary Search Tree](./0700.search-in-a-binary-search-tree)
- [Insert into a Binary Search Tree](./0701.insert-into-a-binary-search-tree)
- [Minimum Distance Between BST Nodes](./0783.minimum-distance-between-bst-nodes)
- [Binary Tree Pruning](./0814.binary-tree-pruning)
- [Leaf-Similar Trees](./0872.leaf-similar-trees)
- [All Possible Full Binary Trees](./0894.all-possible-full-binary-trees)
- [Increasing Order Search Tree](./0897.increasing-order-search-tree)
- [Range Sum of BST](./0938.range-sum-of-bst)
- [Flip Equivalent Binary Trees](./0951.flip-equivalent-binary-trees)
- [Check Completeness of a Binary Tree](./0958.check-completeness-of-a-binary-tree)
- [Univalued Binary Tree](./0965.univalued-binary-tree)
- [Binary Tree Cameras](./0968.binary-tree-cameras)
- [Distribute Coins in Binary Tree](./0979.distribute-coins-in-binary-tree)
- [Vertical Order Traversal of a Binary Tree](./0987.vertical-order-traversal-of-a-binary-tree)
- [Smallest String Starting From Leaf](./0988.smallest-string-starting-from-leaf)
- [Cousins in Binary Tree](./0993.cousins-in-binary-tree)
- [Maximum Binary Tree II](./0998.maximum-binary-tree-ii)
- [Construct Binary Search Tree from Preorder Traversal](./1008.construct-binary-search-tree-from-preorder-traversal)
- [Sum of Root To Leaf Binary Numbers](./1022.sum-of-root-to-leaf-binary-numbers)
- [Maximum Difference Between Node and Ancestor](./1026.maximum-difference-between-node-and-ancestor)
- [Recover a Tree From Preorder Traversal](./1028.recover-a-tree-from-preorder-traversal)
- [Path In Zigzag Labelled Binary Tree](./1104.path-in-zigzag-labelled-binary-tree)
- [Delete Nodes And Return Forest](./1110.delete-nodes-and-return-forest)
- [Lowest Common Ancestor of Deepest Leaves](./1123.lowest-common-ancestor-of-deepest-leaves)
- [Minimum Cost Tree From Leaf Values](./1130.minimum-cost-tree-from-leaf-values)
- [Find Elements in a Contaminated Binary Tree](./1261.find-elements-in-a-contaminated-binary-tree)
## Two Pointers
- [Longest Substring Without Repeating Characters](./0003.longest-substring-without-repeating-characters)
- [Container With Most Water](./0011.container-with-most-water)
- [3Sum](./0015.3sum)
- [3Sum Closest](./0016.3sum-closest)
- [Remove Nth Node From End of List](./0019.remove-nth-node-from-end-of-list)
- [Remove Duplicates from Sorted Array](./0026.remove-duplicates-from-sorted-array)
- [Remove Element](./0027.remove-element)
- [Trapping Rain Water](./0042.trapping-rain-water)
- [Rotate List](./0061.rotate-list)
- [Sort Colors](./0075.sort-colors)
- [Minimum Window Substring](./0076.minimum-window-substring)
- [Remove Duplicates from Sorted Array II](./0080.remove-duplicates-from-sorted-array-ii)
- [Partition List](./0086.partition-list)
- [Merge Sorted Array](./0088.merge-sorted-array)
- [Valid Palindrome](./0125.valid-palindrome)
- [Linked List Cycle](./0141.linked-list-cycle)
- [Linked List Cycle II](./0142.linked-list-cycle-ii)
- [Two Sum II - Input array is sorted](./0167.two-sum-ii-input-array-is-sorted)
- [Minimum Size Subarray Sum](./0209.minimum-size-subarray-sum)
- [Palindrome Linked List](./0234.palindrome-linked-list)
- [Move Zeroes](./0283.move-zeroes)
- [Find the Duplicate Number](./0287.find-the-duplicate-number)
- [Reverse String](./0344.reverse-string)
- [Reverse Vowels of a String](./0345.reverse-vowels-of-a-string)
- [Intersection of Two Arrays](./0349.intersection-of-two-arrays)
- [Intersection of Two Arrays II](./0350.intersection-of-two-arrays-ii)
- [Partition Labels](./0763.partition-labels)
- [Squares of a Sorted Array](./0977.squares-of-a-sorted-array)
- [Interval List Intersections](./0986.interval-list-intersections)
- [Max Consecutive Ones III](./1004.max-consecutive-ones-iii)
- [Count Number of Nice Subarrays](./1248.count-number-of-nice-subarrays)
## Union Find
- [Surrounded Regions](./0130.surrounded-regions)
- [Number of Islands](./0200.number-of-islands)
- [Smallest String With Swaps](./1202.smallest-string-with-swaps)