268. Missing Number

https://leetcode.com/problems/missing-number/

1. Problem

Given an array containing n distinct numbers taken from 0, 1, 2, ..., n, find the one that is missing from the array.

Example 1:

Input: [3,0,1]
Output: 2

Example 2:

Input: [9,6,4,2,3,5,7,0,1]
Output: 8

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

Solution

class Solution {
public:
    int missingNumber(vector<int>& nums) {
        int sum = (1 + nums.size()) * nums.size() / 2;
        for (const auto &n: nums) sum -= n;
        return sum;
    }
};

• #math