Queue using Two Stacks – Java Code & Algorithm

How to implement a queue using two stacks. In this tutorial, We are going to discuss an algorithm and java code to implement a queue using two stacks.

Check for Balanced Parentheses using Stack – Java Code

Write a java code to check for balanced parentheses using stack. Given an expression containing characters ‘{‘,’}’,'(‘,’)’,'[‘,’]’. We have to write a java code to check whether an input string has valid parentheses.

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An input string is valid if:

Open brackets must be closed by the same type of brackets.
Open brackets must be closed in the correct order.

Example –

i) {[]}) – Invalid
ii) {()}[] – Valid

Java Program to Reverse a String using Stack

Write a java program to reverse a string using stack data structure. Given an input string, We have to write a java code to reverse a string using stack.

In my previous tutorial, I have explained java program to reverse a string using recursion.

Before solving this problem, Let’s understand what is a stack data structure.

Find Next Greater Element in an Array – Java Code

Write a java program to find next greater element in an array. Given an input array, find the next greater element for every element of an array.The next greater element x is the first greater element on the right side of x in an array.

For example:

Let’s take an array: [4, 2, 6, 8, 1]

4 => 6 (First next greater element of 4 is 6)
2 => 6 (Next greater element of 2 is 6)
6 => 8 (Next greater element of 6 is 8)
8 => null
1 => null

MCQ on Data Structure – Stack and Queue

MCQ on stack and queue data structure. The concept of Stack and Queue data structure is very important in computer science. In my previous post i have discussed following things.

Stack program in C using Array.

Queue data structure and their implementation.

The purpose of this objective questions is to test how well you understand the concept of stack and queue.

Stack Program in C using an Array – Stack Tutorial Part – I

Write a stack program in C using an array. Implement a stack data structure using an Array. In this tutorial, You are going to learn about stack data structure and it’s implementation in C using an array.

C Program to Implement a Stack using Linked List

What is a Stack Data Structure?

A Stack is a Data Structure, in which insertion and deletion operations are allowed only at one end. It worked on LIFO (Last In First Out) Principle. In LIFO, an element which inserted last must be the first element to be removed.