Missing Number

https://leetcode.com/problems/missing-number/?tab=Description

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?

int missingNumber(int* nums, int numsSize) {
     long long sum = 0;
     for(int i = 0; i < numsSize; i++) sum+=nums[i];
     return numsSize*(numsSize+1)/2 - sum;
}