refactor(algorithms, arrays): remove sorting in place

Author: BrianLusina

algorithms/arrays/non_constructible_change/README.md

@@ -9,12 +9,12 @@ multiple coins of the same value).
 
 Sample Input:
 
-```plain
+```text
 coins = [5,7,1,1,2,3,22]
 ```
 
 Sample output:
 
-```plain
+```text
 20
 ```

algorithms/arrays/non_constructible_change/__init__.py

@@ -3,13 +3,24 @@
 
 def non_constructible_change(coins: List[int]) -> int:
     """
+    Return the smallest amount of change that cannot be created from the given coins.
+    Greedy approach: track the maximum constructible change 'current_change_created'.
+    If the next coin is greater than current_change_created + 1, we've found the gap.
 
+    Examples:
+    >>> non_constructible_change([5, 7, 1, 1, 2, 3, 22])
+    20
+    >>> non_constructible_change([])
+    1
+    >>> non_constructible_change([1, 1, 1, 1, 1])
+    6
     """
-    coins.sort()
+    # Do not mutate the caller's input; iterate over a sorted copy.
+    sorted_coins = sorted(coins)
 
     current_change_created = 0
 
-    for coin in coins:
+    for coin in sorted_coins:
         if coin > current_change_created + 1:
             return current_change_created + 1
         current_change_created += coin

algorithms/arrays/non_constructible_change/test_non_constructible_change.py

@@ -94,6 +94,12 @@ def test_13(self):
         actual = non_constructible_change(coins)
         self.assertEqual(actual, expected)
 
+    def test_input_not_mutated(self):
+       """should not mutate the input coins list"""
+       coins = [5, 7, 1, 1, 2, 3, 22]
+       snapshot = coins[:]
+       _ = non_constructible_change(coins)
+       self.assertEqual(coins, snapshot)
 
 if __name__ == '__main__':
     unittest.main()