Count and Say

 1 class Solution:
 2     # @return a string
 3     def countAndSay(self, n):
 4         if n==1:
 5             return "1"
 6         else:
 7             output=""
 8             res=self.countAndSay(n-1)
 9             n=1
10             i=1
11             while i<len(res):
12                 if res[i-1]==res[i]:
13                     n=n+1
14                 else:
15                     output=output+str(n)+res[i-1]
16                     n=1
17                 i=i+1
18             output=output+str(n)+res[i-1]
19             return output