91 Decode Ways

dp解法 O(1) space

class Solution:# @param {string} s# @return {integer}def numDecodings(self, s):if s == "" or s[0] == "0":return 0dp0, dp1 = 1, 1for i in range(1, len(s)):if s[i] == "0":if s[i-1] == "0" or s[i-1] >= '3':return 0else:dp0, dp1 = dp1, dp0else:if '10' < s[i-1: i+1] < '27':dp0, dp1 = dp1, dp0 + dp1else:dp0 = dp1return dp1

转载于:https://www.cnblogs.com/dapanshe/p/4686074.html

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