Single Number

Introduction

Given a non-empty array of integers, 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?

Example 1:

Input: [2,2,1]
Output: 1

Example 2:

Input: [4,1,2,1,2]
Output: 4

Solution

Golang:

func singleNumber(nums []int) int {

    sum := 0
    for _, n := range nums {
        sum = sum ^ n
    }

    return sum
}

Explanation

If we sum all numbers by using xor operation, then only one will left, because a ^ a = 0.