Package g0001_0100.s0038_count_and_say

Class Solution

java.lang.Object
g0001_0100.s0038_count_and_say.Solution
public class Solution extends java.lang.Object
38 - Count and Say.

Medium

The count-and-say sequence is a sequence of digit strings defined by the recursive formula:

  • countAndSay(1) = "1"
  • countAndSay(n) is the way you would “say” the digit string from countAndSay(n-1), which is then converted into a different digit string.

To determine how you “say” a digit string, split it into the minimal number of groups so that each group is a contiguous section all of the same character. Then for each group, say the number of characters, then say the character. To convert the saying into a digit string, replace the counts with a number and concatenate every saying.

For example, the saying and conversion for digit string "3322251":

Given a positive integer n, return the nth term of the count-and-say sequence.

Example 1:

Input: n = 1

Output: “1”

Explanation: This is the base case.

Example 2:

Input: n = 4

Output: “1211”

Explanation:

 countAndSay(1) = "1"
 countAndSay(2) = say "1" = one 1 = "11"
 countAndSay(3) = say "11" = two 1's = "21"
 countAndSay(4) = say "21" = one 2 + one 1 = "12" + "11" = "1211"

Constraints:

  • 1 <= n <= 30

  • Constructor Summary

    Constructors
    Constructor
    Description
    Solution()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    java.lang.String
    countAndSay(int n)
     

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • countAndSay

      public java.lang.String countAndSay(int n)