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.

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

The original problem is here.

The original code is here.

My Solution

I solve this problem in C++, as below:

*Missing Number 
*Author: shuaijiang
*Email: zhaoshuaijiang8@gmail.com
using namespace std;

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


To solve the problem, first comput the sum of the array 0…n with the missing number. Then add all the number to total, we can get the missing number by sum-total.