Add input validation for capacity and max_items

Author: Hardvan

greedy_methods/fractional_knapsack.py

@@ -34,13 +34,21 @@ def frac_knapsack(
         ...
     ValueError: zip() argument 2 is longer than argument 1
     >>> frac_knapsack([10, 40, 30, 50], [5, 4, 6, 3], 0, 4)
-    0
+    Traceback (most recent call last):
+        ...
+    ValueError: Capacity and max_items must be greater than 0
     >>> frac_knapsack([10, 40, 30, 50], [5, 4, 6, 3], 8, 0)
-    95.0
+    Traceback (most recent call last):
+        ...
+    ValueError: Capacity and max_items must be greater than 0
     >>> frac_knapsack([10, 40, 30, 50], [5, 4, 6, 3], -8, 4)
-    0
+    Traceback (most recent call last):
+        ...
+    ValueError: Capacity and max_items must be greater than 0
     >>> frac_knapsack([10, 40, 30, 50], [5, 4, 6, 3], 8, -4)
-    95.0
+    Traceback (most recent call last):
+        ...
+    ValueError: Capacity and max_items must be greater than 0
     >>> frac_knapsack([10, 40, 30, 50], [5, 4, 6, 3], 800, 4)
     130
     >>> frac_knapsack([10, 40, 30, 50], [5, 4, 6, 3], 8, 400)
@@ -51,6 +59,10 @@ def frac_knapsack(
     TypeError: unsupported operand type(s) for /: 'str' and 'int'
     """
 
+    # Input validation
+    if capacity <= 0 or max_items <= 0:
+        raise ValueError("Capacity and max_items must be greater than 0")
+
     # sort in descending order of value/weight ratio
     r = sorted(
         zip(values, weights, strict=True), key=lambda x: x[0] / x[1], reverse=True