ABCDEFGHIJKLMOPQRSTUVWXYZAA
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ReviewQues.TypeProblem ClassName (with difficulty)Similar ProblemsGood Answer
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2String (Stack)
1249. Minimum Remove to Make Valid Parentheses
20. Valid Parentheses
https://leetcode.com/problems/minimum-remove-to-make-valid-parentheses/discuss/1073189/C%2B%2B-or-2-Approaches-or-O(n)-Beats-100-or-No-Extra-Space-(Best)-or-Explanation
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Linked List (Deep Copy)138. Copy List with Random Pointer
https://leetcode.com/problems/copy-list-with-random-pointer/solutions/169069/copy-list-with-random-pointer/
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String (OOP)1396. Design Underground System
https://leetcode.com/problems/design-underground-system/discuss/554879/C%2B%2BJavaPython-HashMap-and-Pair-Clean-and-Concise-O(1)
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Linked List142. Linked List Cycle IIhttps://leetcode.com/problems/linked-list-cycle-ii/editorial/
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Linked List2. Add Two Numbers
445. Add Two Numbers II
https://leetcode.com/problems/add-two-numbers/solution/201428
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Linked List92. Reverse Linked List II
https://leetcode.com/problems/reverse-linked-list-ii/editorial/?envType=daily-question&envId=2023-09-07
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Linked List24. Swap Nodes in Pairsself-solved but took notes in notebook in section of LinkedList
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2String2343. Query Kth Smallest Trimmed Number
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String6. Zigzag Conversionhttps://leetcode.com/problems/zigzag-conversion/solutions/3465/share-simple-c-solution/
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String (Two Pointer)680. Valid Palindrome IIhttps://leetcode.com/problems/valid-palindrome-ii/discuss/107751/C%2B%2B-clean-solution-O(n)
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2String8. String to Integer (atoi)
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String (Hash Table)916. Word Subsets
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Basic Data Structures
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String68. Text Justification
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String (Counting Sort)49. Group Anagrams
https://leetcode.com/problems/group-anagrams/solutions/19200/c-unordered-map-and-counting-sort/?orderBy=most_votes
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String(IO)290. Word Pattern
https://leetcode.com/problems/word-pattern/solutions/73409/short-c-read-words-on-the-fly/?orderBy=most_votes
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String14. Longest Common Prefix
https://leetcode.com/problems/longest-common-prefix/solutions/391089/c-easy-to-understand-solution-using-sort/
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String(Sort)937. Reorder Data in Log Fileshttps://leetcode.com/problems/reorder-data-in-log-files/solutions/192438/c-o-nlogn-time-o-n-space/
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String(Sort)
1233. Remove Sub-Folders from the Filesystem
https://leetcode.com/problems/remove-sub-folders-from-the-filesystem/solutions/408949/c-short-sorting-o-nlogn/?envType=daily-question&envId=2024-10-25
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2String(Binary Search)1268. Search Suggestions System
https://leetcode.com/problems/search-suggestions-system/solutions/957656/search-suggestions-system/?orderBy=most_votes
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String (Two Pointer)151. Reverse Words in a String
https://leetcode.com/problems/reverse-words-in-a-string/solutions/1531693/c-2-solutions-o-1-space-picture-explain-clean-concise/
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26
Greedy
2279. Maximum Bags With Full Capacity of Rocks
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Greedy55. Jump Game
https://leetcode.com/problems/jump-game/solutions/20917/linear-and-simple-solution-in-c/
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Greedy2405. Optimal Partition of String
https://leetcode.com/problems/optimal-partition-of-string/solutions/3376693/image-explanation-3-approaches-o-1-space-c-java-python/?envType=study-plan-v2&envId=amazon-spring-23-high-frequency
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Array (Greedy)135. Candy
https://www.youtube.com/watch?v=j3fGuonaN_U
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Array (Hash Table)2007. Find Original Array From Doubled Array
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Array (Prefix Sum, Subarray)560. Subarray Sum Equals K
https://leetcode.com/problems/subarray-sum-equals-k/solutions/127728/subarray-sum-equals-k/?orderBy=most_votes
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Array (Prefix Sum, Subarray)974. Subarray Sums Divisible by Khttps://leetcode.com/problems/subarray-sums-divisible-by-k/solutions/217985/java-c-python-prefix-sum/
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Array2214. Minimum Health to Beat Game
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Array88. Merge Sorted Array
https://leetcode.com/problems/merge-sorted-array/editorial/?envType=study-plan-v2&envId=top-interview-150
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Array
2340. Minimum Adjacent Swaps to Make a Valid Array
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Array1331. Rank Transform of an Array
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Prefix Sum1590. Make Sum Divisible by P
560. Subarray Sum Equals K
974. Subarray Sums Divisible by K
https://leetcode.com/problems/make-sum-divisible-by-p/solutions/854895/how-to-approach-this-kind-of-problem-mind-map
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Prefix Sum974. Subarray Sums Divisible by K
https://leetcode.com/problems/subarray-sums-divisible-by-k/solutions/5281639/faster-less-mem-detailed-approach-prefix-sum-python-java-c
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Prefix Sum (deque)862. Shortest Subarray with Sum at Least K
https://leetcode.com/problems/shortest-subarray-with-sum-at-least-k/solutions/6053102/beats-100-00-easy-and-step-by-step-breakdown
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3Two Pointer (array)11. Container With Most Water
https://leetcode.com/problems/container-with-most-water/discuss/6089/Anyone-who-has-a-O(N)-algorithm/161263
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3Two Pointer (array)167. Two Sum II - Input Array Is Sorted
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3Two Pointer (array, hash)15. 3Sum
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2Two Pointer (link list)19. Remove Nth Node From End of List
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Two Pointer (array)31. Next Permutation
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Two Pointer16. 3Sum Closesthttps://leetcode.com/problems/3sum-closest/discuss/7883/C%2B%2B-solution-O(n2)-using-sort
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Two Pointer1089. Duplicate Zeros
https://leetcode.com/problems/duplicate-zeros/solutions/312727/c-java-two-pointers-space-o-1/?orderBy=most_votes
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Two Pointer18. 4Sumhttps://leetcode.com/problems/4sum/solutions/666283/4sum/?orderBy=most_votes
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Two Pointer2491. Divide Players Into Teams of Equal SkillChatGPT
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Two Pointer42. Trapping Rain Waterhttps://leetcode.com/problems/trapping-rain-water/solution/
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Two Pointer (DP)838. Push Dominoes
821. Shortest Distance to a Character
https://leetcode.com/problems/push-dominoes/discuss/132332/JavaC%2B%2BPython-Two-Pointers
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Two Pointer80. Remove Duplicates from Sorted Array II
https://leetcode.com/problems/remove-duplicates-from-sorted-array-ii/solutions/27976/3-6-easy-lines-c-java-python-ruby/comments/119993
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Two Pointer
2422. Merge Operations to Turn Array Into a Palindrome
https://leetcode.com/problems/merge-operations-to-turn-array-into-a-palindrome/solutions/2635801/java-simple-two-pointers-solution-o-n/?envType=study-plan-v2&envId=amazon-spring-23-high-frequency
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Queue (Backtracking)17. Letter Combinations of a Phone Number
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Slide Window567. Permutation in String
https://leetcode.com/problems/permutation-in-string/solutions/5871931/marcus-answer-slide-window-characters-counting
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Advaced Data Structures
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HashSet / HashTable1.Two Sum 15. 3Sum18. 4Sum
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HashSet / HashTable15. 3Sum1.Two Sum
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HashSet / HashTable18. 4Sum1.Two Sum
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HashSet / HashTable
3. Longest Substring Without Repeating Characters
https://www.code-recipe.com/post/longest-substring-without-repeating-characters
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HashSet / HashTable2352. Equal Row and Column Pairs
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HashSet / HashTable1570. Dot Product of Two Sparse Vectors
https://leetcode.com/problems/dot-product-of-two-sparse-vectors/discuss/826785/Javascript-Python3-C%2B%2B-Zip-%2B-Map-solutions
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HashSet / HashTable
659. Split Array into Consecutive Subsequences
https://leetcode.com/problems/split-array-into-consecutive-subsequences/discuss/106514/C%2B%2BPython-Esay-Understand-Solution
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HashSet / HashTable128. Longest Consecutive Sequence
https://leetcode.com/problems/longest-consecutive-sequence/solutions/41057/simple-o-n-with-explanation-just-walk-each-streak
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HashTable(Double linklist)146. LRU Cachehttps://leetcode.com/problems/lru-cache/discuss/45976/C++11-code-74ms-Hash-table-+-List
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HashSet / HashTable
1072. Flip Columns For Maximum Number of Equal Rows
https://leetcode.com/problems/flip-columns-for-maximum-number-of-equal-rows/solutions/1218248/c-hashmap-find-maximum-occuring-pattern-explanation
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2Binary Tree (DFS)
236. Lowest Common Ancestor of a Binary Tree
https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/discuss/65225/4-lines-C%2B%2BJavaPythonRuby
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2Binary Tree (DFS)366. Find Leaves of Binary Tree
https://leetcode.com/problems/find-leaves-of-binary-tree/discuss/83858/C%2B%2B-short-easy-understanding-DFS-solution
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2Binary Tree (DFS)
2096. Step-By-Step Directions From a Binary Tree Node to Another
https://leetcode.com/problems/step-by-step-directions-from-a-binary-tree-node-to-another/discuss/1612105/3-Steps
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Binary Search Tree (DFS - preorders)
426. Convert Binary Search Tree to Sorted Doubly Linked List
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Binary Search Tree
108. Convert Sorted Array to Binary Search Tree
https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/editorial/
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Binary Search Tree
105. Construct Binary Tree from Preorder and Inorder Traversal
https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/editorial/
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Binary Search Tree951. Flip Equivalent Binary Treeschatgpt
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DFS (backtracking)46. Permutations
https://www.geeksforgeeks.org/write-a-c-program-to-print-all-permutations-of-a-given-string/
https://leetcode.com/problems/permutations/discuss/18247/My-elegant-recursive-C%2B%2B-solution-with-inline-explanation
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Binary Search33. Search in Rotated Sorted Array
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Binary Search
34. Find First and Last Position of Element in Sorted Array
https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array/discuss/14717/C%2B%2B-binary-search-solution-(lower_bound-implementation).
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Binary Search
1011. Capacity To Ship Packages Within D Days
https://leetcode.com/problems/capacity-to-ship-packages-within-d-days/solutions/2934252/capacity-to-ship-packages-within-d-days/?orderBy=most_votes
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Binary Search875. Koko Eating Bananashttps://leetcode.com/problems/koko-eating-bananas/editorial/
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Basic Algorithms
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DP2D (1D Input)5. Longest Palindromic Substring
516. Longest Palindromic Subsequence
(Do not use DP, which will cost lots of time) https://www.youtube.com/watch?v=XYQecbcd6_c
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DP509. Fibonacci Number
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DP[harder]1155. Number of Dice Rolls With Target Sum
https://leetcode.com/problems/number-of-dice-rolls-with-target-sum/solutions/355940/c-coin-change-2/?orderBy=most_votes
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DP (LIS)300. Longest Increasing Subsequence
https://leetcode.com/problems/longest-increasing-subsequence/solutions/1326308/c-python-dp-binary-search-bit-segment-tree-solutions-picture-explain-o-nlogn/?orderBy=most_votes
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DP (LIS + LDS)
1671. Minimum Number of Removals to Make Mountain Array
https://leetcode.com/problems/minimum-number-of-removals-to-make-mountain-array/description/comments/1887359
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DP[math]790. Domino and Tromino Tiling
https://leetcode.com/problems/domino-and-tromino-tiling/discussion/comments/1566271 https://leetcode.com/problems/domino-and-tromino-tiling/solutions/116581/detail-and-explanation-of-o-n-solution-why-dp-n-2-d-n-1-dp-n-3/comments/116973
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DP
309. Best Time to Buy and Sell Stock with Cooldown
https://leetcode.com/problems/best-time-to-buy-and-sell-stock-with-cooldown/discussion/comments/1725067
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DP823. Binary Trees With Factors