LeetCode: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 {
    //无序数组  
public:
    int missingNumber(vector<int>& nums) {
        sort(nums.begin(),nums.end());
       
        int i;
        for(i=0;i<nums.size();i++)
        {
            if(nums[i]!=i)
                {
                    return i;
                }
            else continue;
        }
        return i;
       
    }
};