Single Number (LeetCode HashMap)

Question: Given an array of integers, every element appears twice except for one. Find that single one.

Note:
Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

Idea: Bit manipulation. Only the target shows up once, the other elements show up twice. Therefore use exclusive or (XOR) to clean the interference of other elements.

Time: O(n). Space: O(1).

Code: 

 public class Solution {  
   public int singleNumber(int[] A) {  
     int res=0;  
     for(int i:A)  
     {  
       res=res^i;  
     }  
     return res;  
   }  
 }