Stack / Monotonic Stack Pattern

Track candidates with LIFO order or monotonic properties.

#	Title	Difficulty	Topics
20	Valid Parentheses	Easy	stack
32	Longest Valid Parentheses	Hard	stack
71	Simplify Path	Medium	stack
84	Largest Rectangle in Histogram	Hard	stack
85	Maximal Rectangle	Hard	stack
101	Symmetric Tree	Easy	stack
150	Evaluate Reverse Polish Notation	Medium	stack
155	Min Stack	Easy	stack
188	Best Time to Buy and Sell Stock IV	Hard	dynamic programming
224	Basic Calculator	Hard	stack
227	Basic Calculator II	Medium	stack
232	Implement Queue using Stacks	Easy	stack
255	Verify Preorder Sequence in Binary Search Tree	Medium	stack
272	Closest Binary Search Tree Value II	Hard	stack
316	Remove Duplicate Letters	Hard	greedy
331	Verify Preorder Serialization of a Binary Tree	Medium	stack
341	Flatten Nested List Iterator	Medium	stack
385	Mini Parser	Medium	stack
388	Longest Absolute File Path	Medium	hash table
394	Decode String	Medium	stack
439	Ternary Expression Parser	Medium	stack
456	132 Pattern	Medium	stack
496	Next Greater Element I	Easy	stack
503	Next Greater Element II	Medium	stack
636	Exclusive Time of Functions	Medium	stack
654	Maximum Binary Tree	Medium	tree
682	Baseball Game	Easy	stack
726	Number of Atoms	Hard	stack
735	Asteroid Collision	Medium	stack
736	Parse Lisp Expression	Hard	stack
739	Daily Temperatures	Medium	stack
768	Max Chunks To Make Sorted II	Hard	array
770	Basic Calculator IV	Hard	stack
772	Basic Calculator III	Hard	stack
853	Car Fleet	Medium	stack
856	Score of Parentheses	Medium	stack
872	Leaf-Similar Trees	Easy	stack
889	Construct Binary Tree from Preorder and Postorder Traversal	Medium	tree
895	Maximum Frequency Stack	Hard	stack
901	Online Stock Span	Medium	stack
907	Sum of Subarray Minimums	Medium	math
921	Minimum Add to Make Parentheses Valid	Medium	stack
946	Validate Stack Sequences	Medium	stack
962	Maximum Width Ramp	Medium	greedy
975	Odd Even Jump	Hard	dynamic programming
1003	Check If Word Is Valid After Substitutions	Medium	stack
1019	Next Greater Node In Linked List	Medium	stack
1021	Remove Outermost Parentheses	Easy	stack
1047	Remove All Adjacent Duplicates In String	Easy	stack
1063	Number of Valid Subarrays	Hard	stack
1081	Smallest Subsequence of Distinct Characters	Medium	greedy
1130	Minimum Cost Tree From Leaf Values	Medium	stack
1190	Reverse Substrings Between Each Pair of Parentheses	Medium	stack
1209	Remove All Adjacent Duplicates in String II	Medium	stack
1214	Two Sum BSTs	Medium	two pointers
1249	Minimum Remove to Make Valid Parentheses	Medium	greedy
1286	Iterator for Combination	Medium	design
1305	All Elements in Two Binary Search Trees	Medium	two pointers
1340	Jump Game V	Hard	dynamic programming
1373	Maximum Sum BST in Binary Tree	Hard	binary search tree
1377	Frog Position After T Seconds	Hard	depth first search
1379	Find a Corresponding Node of a Binary Tree in a Clone of That Tree	Medium	backtracking
1382	Balance a Binary Search Tree	Medium	binary search tree
1430	Check If a String Is a Valid Sequence from Root to Leaves Path in a Binary Tree	Medium	tree
1441	Build an Array With Stack Operations	Easy	stack
1443	Minimum Time to Collect All Apples in a Tree	Medium	tree
1448	Count Good Nodes in Binary Tree	Medium	tree
1457	Pseudo-Palindromic Paths in a Binary Tree	Medium	tree
1466	Reorder Routes to Make All Paths Lead to the City Zero	Medium	depth first search
1469	Find All The Lonely Nodes	Easy	tree
1475	Final Prices With a Special Discount in a Shop	Easy	array
1485	Clone Binary Tree With Random Pointer	Medium	depth first search
1490	Clone N-ary Tree	Medium	tree
1504	Count Submatrices With All Ones	Medium	dynamic programming
1516	Move Sub-Tree of N-Ary Tree	Hard	tree
1519	Number of Nodes in the Sub-Tree With the Same Label	Medium	tree
1522	Diameter of N-Ary Tree	Medium	tree
1530	Number of Good Leaf Nodes Pairs	Medium	tree
1541	Minimum Insertions to Balance a Parentheses String	Medium	stack
1597	Build Binary Expression Tree From Infix Expression	Medium	stack
1612	Check If Two Expression Trees are Equivalent	Medium	tree
1644	Lowest Common Ancestor of a Binary Tree II	Medium	depth first search
1673	Find the Most Competitive Subsequence	Medium	greedy
1676	Lowest Common Ancestor of a Binary Tree IV	Medium	depth first search
1776	Car Fleet II	Hard	math
1856	Maximum Subarray Min-Product	Medium	stack
1896	Minimum Cost to Change the Final Value of Expression	Hard	dynamic programming
1944	Number of Visible People in a Queue	Hard	stack
1950	Maximum of Minimum Values in All Subarrays	Medium	stack
2003	Smallest Missing Genetic Value in Each Subtree	Hard	tree
2030	Smallest K-Length Subsequence With Occurrences of a Letter	Hard	greedy
2096	Step-By-Step Directions From a Binary Tree Node to Another	Medium	tree
2104	Sum of Subarray Ranges	Medium	stack
2197	Replace Non-Coprime Numbers in Array	Hard	stack
2281	Sum of Total Strength of Wizards	Hard	stack
2282	Number of People That Can Be Seen in a Grid	Medium	stack
2289	Steps to Make Array Non-decreasing	Hard	dynamic programming
2296	Design a Text Editor	Hard	design
2297	Jump Game VIII	Medium	dynamic programming
2334	Subarray With Elements Greater Than Varying Threshold	Hard	stack
2345	Finding the Number of Visible Mountains	Medium	math
2355	Maximum Number of Books You Can Take	Hard	stack
2378	Choose Edges to Maximize Score in a Tree	Medium	dynamic programming
2390	Removing Stars From a String	Medium	string
2454	Next Greater Element IV	Hard	stack
2487	Remove Nodes From Linked List	Medium	linked list
2696	Minimum String Length After Removing Substrings	Easy	stack
2735	Collecting Chocolates	Medium	stack
2736	Maximum Sum Queries	Hard	stack
2751	Robot Collisions	Hard	simulation
2759	Convert JSON String to Object	Hard	design
2764	is Array a Preorder of Some ‌Binary Tree	Medium	stack
2818	Apply Operations to Maximize Score	Hard	binary heap
2832	Maximal Range That Each Element Is Maximum in It	Medium	stack
2863	Maximum Length of Semi-Decreasing Subarrays	Medium	stack
2865	Beautiful Towers I	Medium	stack
2866	Beautiful Towers II	Medium	stack
2876	Count Visited Nodes in a Directed Graph	Hard	graph
2899	Last Visited Integers	Easy	stack
2907	Maximum Profitable Triplets With Increasing Prices I	Medium	binary search tree
2921	Maximum Profitable Triplets With Increasing Prices II	Hard	binary search tree
2926	Maximum Balanced Subsequence Sum	Hard	binary search tree
2940	Find Building Where Alice and Bob Can Meet	Hard	binary search
2945	Find Maximum Non-decreasing Array Length	Hard	dynamic programming
3113	Find the Number of Subarrays Where Boundary Elements Are Maximum	Hard	stack
3170	Lexicographically Minimum String After Removing Stars	Medium	greedy
3174	Clear Digits	Easy	stack
3359	Find Sorted Submatrices With Maximum Element at Most K	Hard	dynamic programming
3412	Find Mirror Score of a String	Medium	simulation
3542	Minimum Operations to Convert All Elements to Zero	Medium	greedy
3555	Smallest Subarray to Sort in Every Sliding Window	Medium	two pointers
3561	Resulting String After Adjacent Removals	Medium	simulation
3676	Count Bowl Subarrays	Medium	stack
3703	Remove K-Balanced Substrings	Medium	stack
3749	Evaluate Valid Expressions	Hard	stack
3814	Maximum Capacity Within Budget	Medium	array
3834	Merge Adjacent Equal Elements	Medium	stack
3878	Count Good Subarrays	Hard	stack