# Single Number

Given `2 * n + 1`

numbers, every numbers occurs twice except one. Find the single number. Can you do it in O(n) time and O(1) space?

Example

Given `[1, 2, 2, 1, 3, 4, 3]`

, return `4`

Given `2 * n + 1`

numbers, every numbers occurs twice except one. Find the single number. Can you do it in O(n) time and O(1) space?

Example

Given `[1, 2, 2, 1, 3, 4, 3]`

, return `4`