def find_odd_occurred_number_sol2(nums):
    """
    You are given an array of repeating numbers. All numbers repeat in even way, except for
    one. Find the odd occurring number.

    - This solution takes less space.
    - More details: https://youtu.be/bMF2fG9eY0A

    - Time: O(len(nums))
    - Space: worst: O(len(nums))
    """
    values = set()
    for value in nums:
        if value in values:
            values.remove(value)
        else:
            values.add(value)

    return next(iter(values))