From 49a1de68061676c6f283b92584efb7f2f125e6d0 Mon Sep 17 00:00:00 2001
From: Janvi Singhal <janvisinghal10@gmail.com>
Date: Mon, 27 Oct 2025 09:22:39 +0530
Subject: [PATCH] Add unique number finder script with input parsing and demo
 functionality

---
 Python/uniqueNo.py | 66 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)
 create mode 100644 Python/uniqueNo.py

diff --git a/Python/uniqueNo.py b/Python/uniqueNo.py
new file mode 100644
index 0000000..4c728d6
--- /dev/null
+++ b/Python/uniqueNo.py
@@ -0,0 +1,66 @@
+
+"""
+uniqueNo.py
+
+Find the unique number in an array where every other element appears exactly twice.
+
+Input (stdin):
+ - First line: optional integer n (number of elements)
+ - Remaining tokens: integers (either n integers, or a list of integers)
+
+Output:
+ - Prints the unique integer (the one that appears once) to stdout.
+
+If no input is provided, a small demo runs.
+"""
+
+import sys
+from typing import Iterable
+
+
+def unique_number(arr: Iterable[int]) -> int:
+	"""Return the unique number when every other number appears exactly twice.
+
+	This uses XOR properties: x ^ x = 0 and x ^ 0 = x, so XORing all numbers
+	leaves the unique value.
+	"""
+	res = 0
+	for x in arr:
+		res ^= x
+	return res
+
+
+def parse_input(stream) -> list:
+	data = stream.read().strip().split()
+	if not data:
+		return []
+	try:
+		nums = [int(tok) for tok in data]
+	except ValueError:
+		raise
+
+	# If first token is count and matches remaining length, skip it
+	if len(nums) >= 2 and nums[0] == len(nums) - 1:
+		return nums[1:]
+	return nums
+
+
+def main() -> int:
+	try:
+		arr = parse_input(sys.stdin)
+	except Exception:
+		print("Error: failed to parse input. Expected integers.")
+		return 1
+
+	if not arr:
+		demo = [2, 3, 5, 4, 5, 3, 4]
+		print("No input detected — running demo array:", demo)
+		print("Unique number:", unique_number(demo))
+		return 0
+
+	print(unique_number(arr))
+	return 0
+
+
+if __name__ == '__main__':
+	raise SystemExit(main())