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

For example,

public class Solution {    public  int missingNumber(int[] nums) {		if (nums == null) {			return 0;		}		int result = 0;		Map
    
      map = new HashMap
     
      ();        for (int  i = 0;  i < nums.length; ++i) {        	map.put(nums[i], 2);        }        for (int i = 0; i <= nums.length; ++i) {        	Integer in = map.get(i);        	if (in == null) {        		return i;        	}        }		return result;    }}
     
    

for (int i = 0; i <= nums.length; ++i) {        	Integer in = map.get(i);        	if (in == null) {        		return i;        	}        }