268. Missing Number.cpp

/*
Problem Description£º
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) {
        int sum=0;
        for(auto num:nums)
        {
            sum+=num;
        }
        return nums.size()*(nums.size()+1)/2-sum;
    }
};