LC-268 Missing Number

# xor
class Solution(object):
    def missingNumber(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        xor, i = 0, 0
        while i < len(nums):
            xor = xor ^ i ^ nums[i]
            i += 1
        return xor ^ i

# sum
class Solution(object):
    def missingNumber(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        n = len(nums)
        sums = (0 + n) * (n + 1) // 2
        for num in nums:
            sums -= num
        return sums

# sort
class Solution(object):
    def missingNumber(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        nums.sort()
        i = 0
        for num in nums:
            if num != i:
                return i
            i += 1
        return i