｀｀｀
class Solution(object):
def numDecodings(self, s):
"""
:type s: str
:rtype: int
"""
if s==''or s[0]=='0':
return 0
d=[1 for i in xrange(len(s)+1)]
for i in xrange(2,len(s)+1):
if (s[i-2]!='0' and s[i-2:i]>'0' and s[i-2:i]<'27'and s[i-1]!='0'):
d[i]=d[i-1]+d[i-2]
elif(s[i-1]=='0'):
if (s[i-2]!='0' and s[i-2:i]>'0' and s[i-2:i]<'27'):
d[i]=d[i-2]
#two consecutive zeros
else:return 0
else: d[i]=d[i-1]
return d[len(s)]
｀｀｀
