Stacks & Queues

Implement Stack from Scratch

Implement Queue from Scratch

Implement 2 stack in an array

find the middle element of a stack

Implement "N" stacks in an Array

Check the expression has valid or Balanced parenthesis or not.

Reverse a String using Stack

Design a Stack that supports getMin() in O(1) time and O(1) extra space.

Find the next Greater element

The celebrity Problem

Arithmetic Expression evaluation

Evaluation of Postfix expression

Implement a method to insert an element at its bottom without using any other data structure.

Reverse a stack using recursion

Sort a Stack using recursion

Merge Overlapping Intervals

Largest rectangular Area in Histogram

Length of the Longest Valid Substring

Expression contains redundant bracket or not

Implement Stack using Queue

Implement Stack using Deque

Stack Permutations (Check if an array is stack permutation of other)

Implement Queue using Stack

Implement "n" queue in an array

Implement a Circular queue

LRU Cache Implementationa

Reverse a Queue using recursion

Reverse the first “K” elements of a queue

Interleave the first half of the queue with second half

Find the first circular tour that visits all Petrol Pumps

Minimum time required to rot all oranges

Distance of nearest cell having 1 in a binary matrix

First negative integer in every window of size “k”

Check if all levels of two trees are anagrams or not.

Sum of minimum and maximum elements of all subarrays of size “k”.

Minimum sum of squares of character counts in a given string after removing “k” characters.

Queue based approach or first non-repeating character in a stream.

Next Smaller Element