amended fibonacci and making change cache

Author: donarbl

Sprint-2/improve_with_caches/fibonacci/fibonacci.py

@@ -1,4 +1,8 @@
-def fibonacci(n):
+def fibonacci(n, cache={}):
     if n <= 1:
         return n
-    return fibonacci(n - 1) + fibonacci(n - 2)
+    if n in cache:
+        return cache[n]
+    result = fibonacci(n - 1) + fibonacci(n - 2)
+    cache[n] = result
+    return result

Sprint-2/improve_with_caches/making_change/making_change.py

@@ -1,22 +1,15 @@
 from typing import List
 
-
 def ways_to_make_change(total: int) -> int:
-    """
-    Given access to coins with the values 1, 2, 5, 10, 20, 50, 100, 200, returns a count of all of the ways to make the passed total value.
-
-    For instance, there are two ways to make a value of 3: with 3x 1 coins, or with 1x 1 coin and 1x 2 coin.
-    """
-    return ways_to_make_change_helper(total, [200, 100, 50, 20, 10, 5, 2, 1])
+    cache = {}
+    return ways_to_make_change_helper(total, (200, 100, 50, 20, 10, 5, 2, 1), cache)
 
-
-def ways_to_make_change_helper(total: int, coins: List[int]) -> int:
-    """
-    Helper function for ways_to_make_change to avoid exposing the coins parameter to callers.
-    """
+def ways_to_make_change_helper(total: int, coins: tuple, cache: dict) -> int:
     if total == 0 or len(coins) == 0:
         return 0
-
+    cache_key = (total, coins)
+    if cache_key in cache:
+        return cache[cache_key]
     ways = 0
     for coin_index in range(len(coins)):
         coin = coins[coin_index]
@@ -26,7 +19,12 @@ def ways_to_make_change_helper(total: int, coins: List[int]) -> int:
             if total_from_coins == total:
                 ways += 1
             else:
-                intermediate = ways_to_make_change_helper(total - total_from_coins, coins=coins[coin_index+1:])
+                intermediate = ways_to_make_change_helper(
+                    total - total_from_coins,
+                    coins=coins[coin_index + 1:],
+                    cache=cache
+                )
                 ways += intermediate
             count_of_coin += 1
-    return ways
+    cache[cache_key] = ways
+    return ways