Missing Number

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?

思路

0-n, 求和相减就OK了
easy

代码

class Solution {public:    int missingNumber(vector<int>& nums) {        int n = nums.size();        int sum = n*(n+1)/2;        int s=0;        for(vector<int>::iterator it=nums.begin();it!=nums.end();it++)            s+=(*it);                return sum-s;    }};