LeetCode136. 只出现一次的数字

思路：异或运算
a^0=a
a^a=0
a ^ b ^ c = a ^ c ^ b

class Solution {
    public int singleNumber(int[] nums) {
        int single = 0;
        for (int num : nums) {
            single ^= num;
        }
        return single;
    }
}