268. Missing Number

1. Question: 268. Missing Number

url : https://leetcode.com/problems/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?

2. Solution:

class Solution(object):
    def missingNumber(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        size = len(nums)
        for i in range(size):
            if nums[i] == size:
                continue
            while nums[i] != i and nums[i] != size:
                if nums[nums[i]] == nums[i]:
                    return i
                nums[nums[i]], nums[i] = nums[i], nums[nums[i]]

        for i in range(size):
            
            if nums[i] != i:
                return i
        return size