Count and Say in Python
Here we will see the Count and Say sequence. This is a sequence whose few terms are like below −
The string will be read like
- 1 (One)
- 11 (One 1) So read the previous 1, and say “One 1”
- 21 (Two 1) So read the previous 11, and say “Two 1”
- 1211 (One 2 one 1) So read the previous 21, and say “One 2 one 1”
- 111221 (One 1 one 2 two 1) So read the previous 1211, and say “One 1 one 2 two 1”
Suppose we have a number n, 1 <= n < = 30, then we have to generate nth term.
To solve this, we will follow this approach −
- set s := “1”
- if n = 1, then return s
- for i := 2 to n + 1
- j := 0, temp := “”, curr = “” and count := 0
- while j < length of s, do
- if curr is “”, then curr := s[j], count := 1 and increase j by 1
- else if curr is s[j], then increase count and j by 1
- otherwise temp := temp + count as string + curr, curr = “”, count := 0
- temp := temp + count as string + curr
- return s
Let us see the following implementation to get better understanding −
Example
Live Demo
class Solution(object):
def countAndSay(self, n):
"""
:type n: int
:rtype: str
"""
s = "1"
if n == 1:
return s
for i in range(2,n+1):
j = 0
temp = ""
curr = ""
count = 0
while j<len(s):
#print(curr,count)
if curr =="":
#print(curr)
curr=s[j]
count=1
j+=1
elif curr == s[j]:
#print(curr)
count+=1
j+=1
else:
#print(count,curr)
temp+= str(count) + curr
curr=""
count = 0
#print(temp)
temp+=str(count) + curr
s=temp
return s
ob1 = Solution()
print(ob1.countAndSay(6))
Input
print(ob1.countAndSay(6))
Output
312211
Published on 08-Jan-2020 15:15:23
