91.md

91 Decode Ways

Description

link

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Solution

• w : current answer of decode ways

• v : previous answer of decode ways

• pre : previous character

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Code

Complexity T : O(n)

class Solution:
    def numDecodings(self, s):
        """
        :type s: str
        :rtype: int
        """
        v, w, pre = 0, int(len(s) > 0), ''
        for c in s:
            v, w, pre = w, (c > '0') * w + (9 < int(pre + c) < 27) * v, c
        return w