Create Decode-Ways.py

Author: AG-Systems

Leetcode/Decode-Ways.py

@@ -0,0 +1,19 @@
+class Solution:
+    def numDecodings(self, s: str) -> int:
+        
+        def helper(s, index, cache):
+            if index == 0:
+                return 1
+            starting_index = len(s) - index
+            if s[starting_index] == "0":
+                return 0
+            if index in cache:
+                return cache[index]
+            
+            result = helper(s, index - 1, cache)
+            if index >= 2 and int(s[starting_index:starting_index + 2]) <= 26:
+                result += helper(s, index - 2, cache)
+            cache[index] = result
+            return result
+        
+        return helper(s, len(s), {})