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.

For example,
Given nums = [0, 1, 3] return 2.

Note:

Your algorithm should run in linear runtime complexity. Could you implement it using only constant extra space complexity?

class Solution {
public:
    int missingNumber(vector<int>& nums) {
        if(nums.size()==0) return 0;
        if(nums.size()==1 && nums[0]==0) return 1;
        if(nums.size()==1 && nums[0]==1) return 0;
        sort(nums.begin(),nums.end());
        for(int i = 0 ;i< nums.size(); i++)
        { 
            if(nums[i] != i)
                return nums[i]-1;
        }
        return nums[nums.size()-1]+1;
    }
};