LeetCode 91. Decode Ways

題目

思路

DP

代碼

class Solution:
    def numDecodings(self, s):
        """
        :type s: str
        :rtype: int
        """
        dp = [0 for i in range(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 '10' <= s[i - 2: i] and s[i - 2: i] <= '26':
                dp[i] += dp[i - 2]
        return dp[len(s)]