Decode Ways (Deprecated)

Given an encoding from letters to numbers, count the number of ways to decode a string of numbers. Tags: Dynamic Programming, Recursion

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Solution

class Solution:
    def numDecodings(self, s: str) -> int:
        dp = [0 for i in range(len(s) + 1)]
        dp[0] = 1
        if 1 <= int(s[0]) <= 9:
            dp[1] = 1
        
        for i in range(2, len(s) + 1):
            if 1 <= int(s[i - 1]) <= 9:
                dp[i] += dp[i - 1]
            if 10 <= int(s[i - 2:i]) <= 26:
                dp[i] += dp[i - 2]
            
        return dp[-1]