Stack
40 problems
Stacks support LIFO (last-in, first-out) operations in O(1). Key patterns: balanced parentheses, next greater element (monotonic stack), function call simulation, and undo/redo. A monotonic stack maintains a strictly increasing or decreasing order to answer range queries efficiently.
- 32.Longest Valid ParenthesesHard
- 85.Maximal RectangleHard
- 114.Flatten Binary Tree to Linked ListMedium
- 144.Binary Tree Preorder TraversalEasy
- 145.Binary Tree Postorder TraversalEasy
- 316.Remove Duplicate LettersMedium
- 321.Create Maximum NumberUnknown
- 331.Verify Preorder Serialization of a Binary TreeUnknown
- 386.Lexicographical NumbersMedium
- 590.N-ary Tree Postorder TraversalEasy
- 678.Valid Parenthesis StringMedium
- 726.Number of AtomsHard
- 769.Max Chunks To Make SortedMedium
- 856.Score of ParenthesesMedium
- 880.Decoded String at IndexMedium
- 921.Minimum Add to Make Parentheses ValidMedium
- 962.Maximum Width RampMedium
- 1081.Smallest Subsequence of Distinct CharactersMedium
- 1106.Parsing A Boolean ExpressionHard
- 1190.Reverse Substrings Between Each Pair of ParenthesesMedium
- 1381.Design a Stack With Increment OperationUnknown
- 1475.Final Prices With a Special Discount in a ShopEasy
- 1526.Minimum Number of Increments on Subarrays to Form a Target ArrayUnknown
- 1574.Shortest Subarray to be Removed to Make Array SortedUnknown
- 1598.Crawler Log FolderEasy
- 1653.Minimum Deletions to Make String BalancedMedium
- 1700.Number of Students Unable to Eat LunchEasy
- 1717.Maximum Score From Removing SubstringsUnknown
- 1963.Minimum Number of Swaps to Make the String BalancedUnknown
- 2116.Check if a Parentheses String Can Be ValidMedium
- 2197.Replace Non-Coprime Numbers in ArrayUnknown
- 2211.Count Collisions on a RoadUnknown
- 2375.Construct Smallest Number From DI StringMedium
- 2434.Using a Robot to Print the Lexicographically Smallest StringMedium
- 2696.Minimum String Length After Removing SubstringsEasy
- 2751.Robot CollisionsUnknown
- 2818.Apply Operations to Maximize ScoreUnknown
- 2940.Find Building Where Alice and Bob Can MeetUnknown
- 3170.Lexicographically Minimum String After Removing StarsUnknown
- 3228.Maximum Number of Operations to Move Ones to the EndUnknown