UVA - 644 - Immediate Decodability

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.LinkedList;

public class Main {

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringBuffer sb = new StringBuffer("");
        String m = "";
        LinkedList<String> list=new LinkedList<String>();
        int cases=1;
        while((m=br.readLine())!=null){
            while(!m.equals("9")){
                list.add(m);
                m=br.readLine();
            }
            String[]arr=new String[list.size()];
            for(int i=0;i<arr.length;i++){
                arr[i]=list.remove();
            }
            boolean pre=false;
            for(int i=0;i<arr.length-1;i++){
                for(int j=i+1;j<arr.length;j++){
                    if(isPrefix(arr[i],arr[j])){
                        pre=true;
                        break;
                    }
                }
                if(pre)
                    break;
            }
            if(pre){
                sb.append("Set ").append(cases).append(" is not immediately decodable\n");
            }
            else{
                sb.append("Set ").append(cases).append(" is immediately decodable\n");
            }
            cases++;
        }
        System.out.print(sb);
    }
   
    static boolean isPrefix(String x,String y){
        for(int i=0,j=0;i<Math.min(x.length(), y.length());i++){
            if(x.charAt(i)!=y.charAt(i)){
                return false;
            }
        }
        return true;
    }
}