## Segregate 0s and 1s in an Array – Java Code

Segregate 0s and 1s in an Array. Given an array of 0s and 1s in random order. Write a java program to segregate 0’s on left side and 1’s on right side of the array.

For example –

Input array = [0, 1, 0, 1, 0, 0, 1]
Output array = [0, 0, 0, 0, 1, 1, 1]

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

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 –

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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.

## 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.

In this tutorial, I am going to explain two approaches and their time complexities to solve this problem. In the first approach, we’ll see how we can find next greater element using two for loops. And after that we can discuss how we can find next greater element using stack.

Also, I have explained how to find next greater element using stack through video tutorial.

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

## Queue Data Structure Implementation Using an Array

Write a program to implement a queue using an array.  In this tutorial, You are going to learn about Queue data structure and their implementation using an array in C, C++ & Java. In my previous posts, I have explained Stack and Linked List data structure.

## Queue Data Structure

In Queue data structure, An element is inserted at one end called rear and deleted at other end called front. As compared to stack data structure in which insertion and deletion are allowed only at one end. Queue data structure is also called FIFO (First In First out).

## Find Common Elements in Two Arrays – Intersection of two Arrays

Write a c program to find common elements in two arrays. Given two positive integer arrays arr1 and arr2 of lengths len1 and len2 we have to write a c code to find intersection of these two arrays. Both the arrays are sorted.

Let’s assume we have following two sorted arrays arr1 and arr2.

int arr1[] = {2,  3,  4,  5,  6};
int arr2[] = {4,  6,  7,  8,  9};

So the common elements in these two arrays is 4 and 6.

## Program to Search an Element in an Array

Write a program to search an element in an array. Given a sorted array, how do you search an element in an array. Think for a moment how do you solve this problem.

You can use multiple approaches to find the solution of this problem. But try to solve this problem in minimum time complexity.

## Find the Second Largest Number in an Array

Write a program to find the second largest number in an array. Given an unsorted array, we have to write a code to find the second largest number in an array. Also, we need to focus on time complexity. As the time complexity of an algorithm is very important in terms of an interview.

For example – Let’s take an array.

Input – arr[] = { 4, 1, 5, 2, 8, 0, 3, 55}

Output – 8

The second largest element in this array is 8.  Think for a moment, how do you find the second largest number in an array?  There are multiple ways to solve this problem. Which approach you prefer and why?

In this tutorial, we cover following things –

• How to find the second largest number in an array using sorting.
• C program to find the second largest number in an array.
• C++ program to find the second largest number in an array.

## How to Find Duplicates in Array

Given an unsorted array. How to find duplicates in array using PHP. These types of questions are generally asked in interviews. Sometimes interviewer allows to use in-built function sometimes not.

## C Program to Find Missing number in Array

Write a c program to find missing number in array. Given an array of numbers from 1 to n. The array is sorted. One number is missing from an array. You have to write a c code to find the missing number from an array. Also ,there is no duplicates in an array. This type of questions is generally asked in technical interviews

## C Program to Reverse a String using Stack, Pointers, Recursion & Swap

Write a c program to reverse a string without using strrev function. Given an input string, we have to write a method to reverse a string. In c, you can simply reverse a string using an inbuilt strrev() function. But we don’t have to use this method.

Think how do you solve this problem. In this tutorial, we write a c code to reverse a string using stack, pointers, recursion, loop.