lintcode-196. Find the Missing Number

Given an array contains N numbers of 0 .. N, find which number doesn't exist in the array.

Example

Given N = 3 and the array [0, 1, 3], return2.

求出给定数组中所有元素之和，再求出从1到数组长度的所有数之和，二者作差即可

class Solution {public:    /*     * @param nums: An array of integers     * @return: An integer     */    int findMissing(vector<int> nums) {        // write your code here        int sum=0;        for(int i=0;i<nums.size();++i)        {            sum+=nums[i];        }        int s=(1+nums.size())*nums.size()/2;        return s-sum;    }};