# Find the number occurring odd number of times in an array

If you want to practice data structure and algorithm programs, you can go through data structure and algorithm interview questions.

In this post, we will see how to find number occurring odd number of times in the array.

### Problem:

You are given a array of integer. All numbers occur even number of times except one. You need to find the number which occurs odd number of time. You need to solve it with o(n) time complexity and o(1) space complexity.
For example:

### Solution:

#### Solution 1: Use two for loops and compare elements:

This is brute force solution for this problem but it takes o(n*n) time complexity.

#### Solution 2 : Use Hashing

You can use key as number and count as value and whenever key is repeated , you can increment counter by 1.

but above solution takes o(n) of space complexity.

#### Solution 3: Use XOR operation:

You can do bitwise XOR operation for all elements  and it will give you element which occurs odd number of times in the end.

Above algorithms solves the problem with O(n) time complexity and o(1) space complexity and this is best solution for above program.

### Java program to find the number occurring odd number of times in an array:

When you run above program, you will get below output:

import_contacts

## Related Posts

• 04 June

### Search for a range Leetcode – Find first and last position of element in sorted array

Table of ContentsApproach 1 (Using Linear Search)Approach 2 (Using Modified Binary Search-Optimal) In this article, we will look into an interesting problem asked in Coding Interviews related to Searching Algorithms. The problem is: Given a Sorted Array, we need to find the first and last position of an element in Sorted array. This problem is […]

• 28 March

### Sort an array of 0s, 1s and 2s

Table of ContentsProblemSolution If you want to practice data structure and algorithm programs, you can go through Java coding interview questions. In this post, we will see how to sort an array of 0s, 1s and 2s.We have already seen a post on sort 0s and 1s in an array. Problem Given an array containing zeroes, […]

• 04 March

### Check if it is possible to reach end of given Array by Jumping

Table of ContentsProblemSolution If you want to practice data structure and algorithm programs, you can go through Java coding interview questions. ﻿ ﻿ Problem Given an array with positive integers as elements indicating the maximum length of a jump which can be made from any position in the array. Check if it is possible to have […]

• 17 February

### Check if Array Elements are Consecutive

Table of ContentsProblemSolutionProgram to check if Array Elements are Consecutive If you want to practice data structure and algorithm programs, you can go through 100+ data structure and algorithm programs. In this post, we will see how to check if array elements are consecutive. Problem Given an array, we need to check if array contains […]

• 01 November

### Find the local minima in array

Table of ContentsProblemSolutionNaive approachEfficient approach If you want to practice data structure and algorithm programs, you can go through Java coding interview questions. In this post, we will see how to find the local minima in the array. Problem An element is local minima if it is less than its neighbors. int [] arr = {10, […]

• 22 October

### Sliding Window Maximum in java

Table of ContentsProblemSolution If you want to practice data structure and algorithm programs, you can go through Java coding interview questions. In this post, we will see about Sliding Window Maximum in java Problem Given an Array of integers and an Integer k, Find the maximum element of from all the contiguous subarrays of size K. […]

## Subscribe to our newletter

Get quality tutorials to your inbox. Subscribe now.