268. Missing Number.py

# coding: utf-8

# In[ ]:


'''
268. Missing Number
Given an array containing n distinct numbers taken from 0, 1, 2, ..., n, find the one that is missing from the array.

Example 1:

Input: [3,0,1]
Output: 2
Example 2:

Input: [9,6,4,2,3,5,7,0,1]
Output: 8
Note:
Your algorithm should run in linear runtime complexity. Could you implement it using only constant extra space complexity?
'''

class Solution:
    def missingNumber(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        
        
        """
        n = len(nums) 
        sumresult = int((n+1)*n/2)
        for i in nums:
            sumresult-=i
        return sumresult
        """
        
        result = len(nums)
        for i in range(len(nums)):
            result^=i^nums[i]
        return result