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?
求出数组中只出现了一次的数（其他的数都出现了2次）
异或求解。
public class Solution {
public int singleNumber(int[] nums) {
int len = nums.length;
int result = nums[0];
for( int i = 1;i<len;i++){
result = result^nums[i];
}
return result;
}
}