gistfile1.java

package ge.code.topcoder;

public class BinaryCode {
	
	private static final String NONE = "NONE";
	
	private int toInt(char c) {
		return Integer.parseInt(Character.toString(c));
	}
	
	private String decode(String message, int startBit) {
		
		StringBuilder decoded = null;
		int l = message.length();
		int[] p = new int[l];
		p[0] = startBit;
		
		for (int i = 0, j = 1, q = 0, p1 = 0, p2 = startBit; i < l; i++, j++, p1 = p2, p2 = q) {
			q = toInt(message.charAt(i)) - p2 - p1;
			if (q > 1 || q < 0) {
				decoded = new StringBuilder(NONE);
				break;
			}
			if (j < l) {
				p[j] = q;
			}
		}
		
		if (decoded == null) {
			decoded = new StringBuilder(p.length);
			for (int i = 0; i < p.length; i++) {
				decoded.append(p[i]);
			}
		}
		
		return decoded.toString();
		
	}
	
	public String[] decode(String message) {		
		return new String[]{
			decode(message, 0),
			decode(message, 1)
		};		
	}
	
	public static void main(String[] args) {
		
		BinaryCode bc = new BinaryCode();		
		String[] result = bc.decode("12221112222221112221111111112221111");
		
		for (int i = 0; i < result.length; i++) {
			System.out.println(result[i]);
		}
		
	}

}