<filename>Week 5/id_355/leetcode91.py
class Solution(object):
    def numDecodings(self, s):
        if s == "": return 0
        dp = [0] * (len(s)+1)
        dp[0] = 1
        for i in range(1, len(s)+1):
            if s[i-1] != "0":
                dp[i] = dp[i-1]
            if i != 1 and s[i-2:i] < "27" and s[i-2:i] > "09":
                dp[i] += dp[i-2]
        return dp[len(s)]
<filename>Week 5/id_355/leetcode91.py
class Solution(object):
    def numDecodings(self, s):
        if s == "": return 0
        dp = [0] * (len(s)+1)
        dp[0] = 1
        for i in range(1, len(s)+1):
            if s[i-1] != "0":
                dp[i] = dp[i-1]
            if i != 1 and s[i-2:i] < "27" and s[i-2:i] > "09":
                dp[i] += dp[i-2]
        return dp[len(s)]