Stack Data Structure

A Stack is a linear data structure that follows a particular order in which the operations are performed. The order is LIFO(Last In First Out) which implies that the element that is inserted last, comes out first.

It behaves like a stack of plates, where the last plate added is the first one to be removed. Pushing an element onto the stack is like adding a new plate on top. Popping an element removes the top plate from the stack.

Basics

• Introduction
• Applications
• Array Implementation
• Linked List Implementation
• Implementation using Deque

Implementations in Different Languages

• Stack in C++ STL
• Stack in Java
• Stack in Python
• Stack in C#
• Stack in JavaScript
• Stack in C

Easy Problems

• The Celebrity Problem
• Queue using Stacks
• Two stacks in an array
• Infix to Postfix
• Prefix to Infix
• Prefix to Postfix
• Postfix to Prefix
• Postfix to Infix
• Infix To Prefix
• Check for balanced parentheses
• Evaluation of Postfix Expression
• Reverse a stack using recursion
• Reversing the first K of a Queue
• A DS with O(1) Operations

Medium Problems

• k Stacks in an Array
• Mergable Stack
• Stack using Queues
• Previous Smaller Element
• Next Greater Element
• Stock Span Problem
• Buildings Facing Sun
• Next Smaller of next Greater
• Next Greater Frequency
• Max product of indexes of greater on left and right
• Iterative Tower of Hanoi
• Sort a Stack
• Reverse a Stack
• Delete middle of a stack
• Check for queue sortable
• Check for stack sortable
• Index of closing bracket for a given opening bracket
• Max Diff between nearest left and right smaller
• Delete consecutive same words

Hard Problems

• Largest Rectangle in a Histogram
• Sum of Max of all Subarrays
• Max of Mins of every window size
• Stack that supports getMin()
• Stack with max frequency
• Longest valid substring
• Check Redundant Bracket
• Stack Permutations
• Remove brackets containing + and – operators

Quick Links :

• Practice Coding on Stack
• Quiz on Stack
• DSA Tutorial