## 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.

## Find Common Elements in Three Sorted Arrays – Java Code

Write a java program to find common elements in three sorted arrays. Given three sorted arrays, write a code to print intersection of three sorted arrays.

For example –

arr1 = {1, 5, 10, 20, 40, 80};
arr2 = {6, 7, 20, 80, 100};
arr3 = {3, 4, 15, 20, 30, 70, 80, 120};

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Output : {20, 80}

20 and 80 is the common element between three sorted arrays.

## Get Minimum Element from Stack in O(1)

Design a stack to get minimum element from stack in O(1) (constant time).

For example : Suppose, If we push following elements in a stack.

9  ==> Top
1
2
3

Then if we call getMin() method, It should return 1 in O(1) (constant time). In a stack, Element which pushed last in the stack is the first element to be popped out. Think for a moment how we can solve this problem.

## Find Middle Element of a Linked List – Java Code

In this tutorial, We are going to explain how to find middle element of a linked list in Java. This programming question is mostly asked in a technical interviews.

For example: Given a linked list, the middle element in this linked list is 8.

15 -> 9 -> 8 -> 5 -> 6 -> NULL

There are multiple approaches to solve this problem. In this tutorial, We are going to learn two approaches through which we can find middle element of a singly linked list. Also, i have also added video tutorial at the end of this tutorial.

## 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.