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?

利用数组和

class Solution {
public:
    int missingNumber(vector<int>& nums)
    {
        int l = nums.size();
        int n = l + 1;
        int sum = (n - 1)* n / 2;
        int tmp = 0;
        for(int i = 0; i < nums.size(); ++i)
        {
            tmp += nums[i];
        }
        return sum - tmp;   
    }
};