fibonacci calculation - use memoization to prevent duplicate calculations.

wdhowe · wdhowe · commit 6d2bec745e08 · 2020-03-03T19:07:09.000-06:00
diff --git a/fast_fibonacci.py b/fast_fibonacci.py
@@ -0,0 +1,33 @@
+#!/usr/bin/env python3
+
+"""
+Using memoization to speed up fibonacci calculations.
+Records computed fib values in a dictionary to prevent duplicate compute time
+"""
+
+
+def fib_memo(num, memo=None):
+    """
+    Assume num >= 0
+    memo is a dictionary used to prevent duplicate calcuations
+    """
+
+    if memo is None:
+        # dictionary not created yet
+        memo = {}
+    if num == 0 or num == 1:
+        # fibonacci base case
+        return 1
+    try:
+        # attempt to lookup the result
+        return memo[num]
+    except KeyError:
+        # result not caculated yet, perform calculation
+        result = fib_memo(num - 1, memo) + fib_memo(num - 2, memo)
+        # store result in dictionary
+        memo[num] = result
+        return result
+
+
+print(f"-> Fib of 5 is: {str(fib_memo(5))}")
+print(f"-> Fib of 100 is: {str(fib_memo(100))}")
