# Problem 40

#### Description

This problem was asked by Google.

Given an array of integers where every integer occurs three times except for one integer, which only occurs once, find and return the non-duplicated integer.

For example, given `[6, 1, 3, 3, 3, 6, 6]`

, return `1`

. Given `[13, 19, 13, 13]`

, return `19`

.

Do this in `O(N)`

time and `O(1)`

space.