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

 

Given N = 3 and the array [0, 1, 3], return 2. 

 

 

public class Solution {    /**         * @param nums: an array of integers     * @return: an integer     */    public int findMissing(int[] nums) {        // write your code here                if(nums == null || nums.length == 0)                return 0;                int sum = 0;                for(int i = 0; i < nums.length; i++){            sum += nums[i];        }                int N = nums.length;                return N * (N + 1) / 2 - sum;            }}