A message containing letters from A-Z
is being encoded to numbers using the following mapping:
‘A‘ -> 1 ‘B‘ -> 2 ... ‘Z‘ -> 26
Given an encoded message containing digits, determine the total number of ways to decode it.
For example,
Given encoded message "12"
, it could be decoded as "AB"
(1 2) or "L"
(12).
The number of ways decoding "12"
is 2.
DP,方法感觉有点像Fobinacci
1 class Solution(object): 2 def numDecodings(self, s): 3 if s==‘‘ or s[0]==‘0‘: return 0 4 r1,r2 = 1,1 5 for i in range(1,len(s)): 6 if s[i] == ‘0‘: 7 r1 = 0 8 if s[i-1:i+1]<‘27‘: 9 r1,r2 = r1+r2,r1 10 else: 11 r2= r1 12 return r1 13
时间: 2024-10-25 08:57:02