top of page

### Looking to master object-oriented and system design for tech interviews or career growth?

• Improve your system design and machine coding skills.

• Study with our helpful resources.

• Prepare for technical interviews and advance your career.

**We're in beta mode and would love to hear your feedback.

Search

# Single Number - InterviewBit Solution

Problem: Single Number

### Problem Description

Given an array of integers A, every element appears twice except for one. Find that single one. NOTE: Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

Problem Constraints

• 2 <= |A| <= 2000000

• 0 <= A[i] <= INTMAX

Input Format

The first and only argument of input contains an integer array A.

Output Format

Return a single integer denoting the single element.

Example Input

Input 1: A = [1, 2, 2, 3, 1] Input 2: A = [1, 2, 2]

Example Output

Output 1: 3 Output 2: 1

Example Explanation

```Explanation 1:
3 occurs once.

Explanation 2:
1 occurs once.```

### Solution Approach:

• If we Xor a number with itself it returns 0. That means a^a = 0

• If we Xor any number with zero we get that number itself. That means a^0 = a.

Considering the above two points we can get the unique number if we xor all the elements of the given array.

### Solution:

Code in C++:

If you have any questions or queries, feel free to drop a comment in the comments section below.

bottom of page