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  Question 2: Single Number in List of Duplicates
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FULL QUESTION:
We provide you with a list of integers. In this list, every number appears twice,
except for one number that appears only once. Your task is to find that single,
unique number.

Example:
- If the list is [4, 1, 2, 1, 2], the unique number is 4.
- If the list is [7, 3, 5, 4, 5, 3, 4], the unique number is 7.

Constraints:
- You should try to solve this with a time complexity of O(n) (linear time).
- You should try to solve this without using extra space (O(1) space complexity),
  meaning no additional data structures like hash maps or sets.

SHORT QUESTION:
Finds the single unique number in a list where all other numbers appear twice, using O(n) time and O(1) space via bitwise XOR.

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README & SETUP INSTRUCTIONS:
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# Question 2: Single Number in List of Duplicates

- Prerequisites: Python 3.x (Standard library only).
- Setup: None.
- How to Run: python question_02.py
- Expected Behavior: Computes and prints the unique single number using bitwise XOR reduction.

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SOURCE CODE FILES:
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1. question_02.py
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numbers = [7, 3, 5, 4, 5, 3, 4]
unique = 0

for i in numbers:
    unique = unique ^ i

print("Unique Number:", unique)
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