You are given an array nums consisting of positive integers, where every integer appears either once or twice.

Return the bitwise XOR of all elements that appear twice in nums. If no number appears twice, return $0$.

Constraints:

• $1 \leq$ nums.length $\leq 50$

• $1 \leq$ nums[i] $\leq 50$

• Each number in nums appears either once or twice.

Now, let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Implement your solution in the following coding playground.