Sponsored
This approach involves constructing the sequence iteratively. We start from the base case, which is '1', and iteratively build up the strings by counting and saying the digits from the last constructed string.
Time Complexity: O(2^n) as the length of the string grows exponentially.
Space Complexity: O(2^n) for storing the string.
1#include <iostream>
2#include <string>
3using namespace std;
4
5string countAndSay(int n) {
6 string result = "1";
7 for (int i = 1; i < n; i++) {
8 string temp = "";
9 for (int j = 0; j < result.length(); ) {
10 char current_digit = result[j];
11 int count = 0;
12 while (j < result.length() && result[j] == current_digit) {
13 count++;
14 j++;
15 }
16 temp += to_string(count) + current_digit;
17 }
18 result = temp;
19 }
20 return result;
21}
22
23int main() {
24 cout << countAndSay(4) << endl;
25 return 0;
26}The C++ solution uses a similar approach to the C solution. It uses std::string for easy string manipulation and resizes dynamically as the sequence progresses.
The recursive approach defines the function countAndSay recursively by computing countAndSay(n-1), then generating the count-and-say encoding for it.
This method involves less memory usage on the function stack compared to an iterative approach but still leverages recursion for elegance.
Time Complexity: O(2^n) as strings grow exponentially.
Space Complexity: O(2^n) due to storing strings and O(n) recursion stack.
1
JavaScript uses recursion where nextSequence operates as a transition function producing each subsequent numeral description recursively.