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Count and Say in Python
Here we will see the Count and Say sequence. This is a sequence whose few terms are like below −
- 1
- 11
- 21
- 1211
- 111221
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
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
Updated on: 28-Apr-2020
923 Views
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