/***
 * 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?
 */
public class Solution {

    public int singleNumber(int[] A) {
        int ret = A[0];
        for (int i = 1; i < A.length; i++){
            ret ^= A[i];
        }
        return ret;

    }

}
