"""
Description:
Given a non-empty array of integers, every element appears twice except for one. Find
that single one. The algorithm should have a linear runtime complexity.

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

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

def singleNumber(nums):
    """
    :type nums: List[int]
    :rtype: int
    """
    v = 0
    for num in nums:
        v ^= num
    return v