codewars #50 String -> N iterations -> String (5kyu)

#50 String -> N iterations -> String

Welcome

This kata is inspired by This Kata

We have a string s

We have a number n

Here is a function that takes your string, concatenates the even-indexed chars to the front, odd-indexed chars to the back.

Examples

s = "Wow Example!"

result = "WwEapeo xml!"

s = "I'm JomoPipi"

result = "ImJm ii' ooPp"

The Task:

return the result of the string after applying the function to it n times.

example where s = "qwertyuio" and n = 2:

after 1 iteration  s = "qetuowryi"

after 2 iterations s = "qtorieuwy"

return "qtorieuwy"

Note

There are 50000 random tests where

the string contains between 50 and 200 chars

n is greater than a billion

so be ready to optimize.

public class JomoPipi {

	public static String sort(String s) {
		StringBuilder odd = new StringBuilder();
		StringBuilder even = new StringBuilder();

		for (int i = 0; i < s.length(); i++) {
			if (i % 2 == 0) {
				odd.append(s.charAt(i));
			} else {
				even.append(s.charAt(i));
			}
		}
		return odd.append(even.toString()).toString();

	}

	public static String jumbledString(String s, long n) {
		String origin = s;
		int cycle = 1;

		for (int i = 0; i < n; i++) {
			s = sort(s);
			if (s.equals(origin)) {
				cycle = i;
				break;
			}
		}
		n %= cycle;
		if (n == 0)
			return s;
		n += 1;
		for (int i = 0; i < n; i++) {
			origin = sort(origin);
		}
		return origin;
	}
}