Single Number

https://leetcode.com/problems/single-number/description/

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?

Thoughts

A XOR A == 0, A XOR B XOR A = B.

Code

class Solution {
    public int singleNumber(int[] nums) {
        int res = nums[0];
        for (int i = 1; i < nums.length; i++) {
            res = res ^ nums[i];
        }
        return res;
    }
}

Analysis

时间复杂度O(n), 空间O(1).