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.

## Solution: XOR

single_number ^ a ^ b ^ c ^ … ^ a ^ b ^ c … = single_number

Time complexity: O(n)
Space complexity: O(1)

## Related Problems

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