0136. Single Number

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

Description

Given a non-empty array of integers nums, every element appears twice except for one. Find that single one.

You must implement a solution with a linear runtime complexity and use only constant extra space.

Example 1:

**Input:** nums = [2,2,1]
**Output:** 1

Example 2:

**Input:** nums = [4,1,2,1,2]
**Output:** 4

Example 3:

**Input:** nums = [1]
**Output:** 1

Constraints:

• 1 <= nums.length <= 3 * 104

• -3 * 104 <= nums[i] <= 3 * 104

• Each element in the array appears twice except for one element which appears only once.

ac

// b ^ b == 0, 0 ^ k == k, a ^ b ^ a ^ b ^ k == a ^ a ^ b ^ b ^ k == k
class Solution {
    public int singleNumber(int[] nums) {
        int res = 0;
        for (int i : nums) {
            res ^= i;
        }
        return res;
    }
}