Count and Say Sequence

Write a C program to generate the nth term of the "Count and Say" sequence. 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 substrings such that each substring contains exactly one unique digit. Then for each substring, say the number of digits, followed by the digit. Finally, concatenate every said digit.

For example, the saying and conversion for digit string "3322251":
Two 3's, three 2's, one 5, and one 1 becomes "23321511".

Example 1

  
Input: n = 1
  
Output: "1"
  
Explanation:

Step 1: countAndSay(1) = "1" (base case)

Example 2

  
Input: n = 4
  
Output: "1211"
  
Explanation:

Step 1: countAndSay(1) = "1" (base case)

Step 2: countAndSay(2) = say "1" = one 1 = "11"

Step 3: countAndSay(3) = say "11" = two 1's = "21"

Step 4: countAndSay(4) = say "21" = one 2 followed by one 1 = "1211"

Constraints

  
1 ≤ n ≤ 30
  
The answer string will only contain digits
  
Time Complexity: O(2^n) - since the length of the result can grow exponentially
  
Space Complexity: O(2^n) - to store the result string