Solve : Decode Ways

Author: printjin-gmailcom

decode-ways/printjin-gmailcom.py

@@ -0,0 +1,13 @@
+class Solution:
+    def numDecodings(self, s):
+        if not s:
+            return 0
+        dp = [0] * (len(s) + 1)
+        dp[0] = 1 
+        dp[1] = 1 if s[0] != '0' else 0 
+        for i in range(2, len(s) + 1):
+            if '1' <= s[i - 1] <= '9':
+                dp[i] += dp[i - 1]
+            if '10' <= s[i - 2:i] <= '26':
+                dp[i] += dp[i - 2]
+        return dp[len(s)]