Implement a method to perform basic string compression using the counts of repeated characters. For example, the string aabcccccaaa would become a2blc5a3. If the "compressed" string would not become smaller than the original string, your method should return the original string.

CC150-1.5.java

public class Main {

	/**
	 * @Runtime & spaces ||runtime: O(n) ||space: O(n)
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Main so = new Main();
		String s = "a";
		System.out.println(so.compress(s));
	}

	public String compress(String s) {
		if (s == null || s.length() == 0)
			return s;
		//use StringBuffer other than String to save time and space
		StringBuffer result = new StringBuffer();
		char last = s.charAt(0);
		int count = 1;
		for (int i = 1; i < s.length(); i++) {
			if (s.charAt(i) == last) {
				count++;
			} else {
				result.append(last);
				result.append(count);
				last = s.charAt(i);
				count = 1;
			}
		}
		result.append(last);
		result.append(count);
		if (result.length() >= s.length())
			return s;
		return result.toString();
	}
}