Stack Interview Questions

LIFO structures for parsing, monotonic stacks, and nested structures.

73 problems

#	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
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
331	Verify Preorder Serialization of a Binary Tree	Medium	stack
341	Flatten Nested List Iterator	Medium	stack
385	Mini Parser	Medium	stack
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
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
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
895	Maximum Frequency Stack	Hard	stack
901	Online Stock Span	Medium	stack
921	Minimum Add to Make Parentheses Valid	Medium	stack
946	Validate Stack Sequences	Medium	stack
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
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
1441	Build an Array With Stack Operations	Easy	stack
1541	Minimum Insertions to Balance a Parentheses String	Medium	stack
1597	Build Binary Expression Tree From Infix Expression	Medium	stack
1856	Maximum Subarray Min-Product	Medium	stack
1944	Number of Visible People in a Queue	Hard	stack
1950	Maximum of Minimum Values in All Subarrays	Medium	stack
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
2334	Subarray With Elements Greater Than Varying Threshold	Hard	stack
2355	Maximum Number of Books You Can Take	Hard	stack
2454	Next Greater Element IV	Hard	stack
2696	Minimum String Length After Removing Substrings	Easy	stack
2735	Collecting Chocolates	Medium	stack
2736	Maximum Sum Queries	Hard	stack
2764	is Array a Preorder of Some ‌Binary Tree	Medium	stack
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
2899	Last Visited Integers	Easy	stack
3113	Find the Number of Subarrays Where Boundary Elements Are Maximum	Hard	stack
3174	Clear Digits	Easy	stack
3676	Count Bowl Subarrays	Medium	stack
3703	Remove K-Balanced Substrings	Medium	stack
3749	Evaluate Valid Expressions	Hard	stack
3834	Merge Adjacent Equal Elements	Medium	stack
3878	Count Good Subarrays	Hard	stack