leetcode38. Count and Say

The count-and-say sequence is the sequence of integers beginning as follows:

1, 11, 21, 1211, 111221, …

1 is read off as “one 1” or 11.

11 is read off as “two 1s” or 21.

21 is read off as “one 2, then one 1” or 1211.

class Solution(object):
def show(self,s):
count=1
ret=''
flag=s[0]
for i in range(1,len(s)):
if s[i]!=flag:
ret=ret+str(count)+flag
flag=s[i]
count=1
else:
count=count+1
ret=ret+str(count)+flag
return ret
def countAndSay(self, n):
"""
:type n: int
:rtype: str
"""
s='1'
if n==1:
return s
else:
for i in range(2,n+1):
s=self.show(s)
return s