Category Archives: Java

Find Middle Element of a Linked List – Java Code

  By | , , |Last updated on: January 7, 2019
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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.

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Java Program to Reverse a String using Stack

  By | , , |Last updated on: November 6, 2018
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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.

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

Find Pairs with Given Sum in a Sorted Array – Java Code

  By | , , |Last updated on: October 14, 2018
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Java code to find pairs with given sum in a sorted array. Given an array A of size N. Write a java code to find all pairs in the array that sum to a number equal to K. If no such pair exists then output will be –1.  Array elements are distinct and in a sorted order.

For example –

Input :

arr[] = {1, 2, 3, 4, 5, 6, 7};
sum = 9

Output:

Pairs with given sum 9 is

Pair (2 , 7 )
Pair (3 , 6 )
Pair (4 , 5 )

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Find First and Last Position of a Number in a Sorted Array – Java Code

  By | , |Last updated on: December 30, 2018
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Given a sorted array which contains duplicate elements, Write a java code to find first and last position of a number in a sorted array. Given a number x, write a code to find it’s first and last index in an array.

For example –

Suppose the input array is arr[] : {1, 4, 7, 8, 8, 11, 11, 11, 11, 12, 13, 13} and the number to be searched is 11. Then the first index of 11 is 5 and last index is 8.

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