The Unpaired Badge
At the end of the day every visitor badge id in the log appears exactly twice (check-in and check-out), except one badge that was never returned and appears once.
Return that id using O(1) extra memory.
Example 1
Input: ids = [4, 1, 2, 1, 2] Output: 4
Example 2
Input: ids = [7] Output: 7
Constraints
- 1 <= ids.length <= 10^5 (odd)
- -10^6 <= ids[i] <= 10^6
- Exactly one id appears once; all others appear twice.
Hint 1
XOR of a number with itself is 0, and XOR with 0 changes nothing.
Hint 2
XOR is order-independent, so XOR everything together.
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Good practice for: Embedded Systems Engineer, Game Developer, Backend Developer, Blockchain Developer, Automation Test Engineer
Run checks your code on 2 sample tests. Submit runs all 6 tests, including hidden ones, and earns points. Use console.log to debug. Python's first run can take a few seconds while it starts.