JAVA:

import java.io.BufferedReader; import java.io.FileReader; import java.io.IOException; import java.util.ArrayList; import java.util.Collections;

public class Main {

public static void main(String[] args) {

    int i=0;

    ArrayList<Prisoner> prisoners = readFromFile("hats.txt");

Collections.reverse(prisoners);

/**
 * What the first prisoner sees. 
 */
boolean first = prisoners.get(0).getOddAhead();

boolean oddPassed= false;
boolean says = false;

for(Prisoner p: prisoners){
    System.out.print("prisoner "+(i++)+": "+(p.getColor()?"white":"black"));
    says = p.findColor(oddPassed, first);
    System.out.println("  says : "+ (says?"white":"black")+"  lives? "+(says==p.getColor()));
    if(says!=p.getColor()){
        System.err.println("DIED");
    }
    oddPassed = (oddPassed^says);
}

}

/** * * @param filename String, name of the file to read the data from. * @return */ static private ArrayList<Prisoner> readFromFile(String filename){

ArrayList<Prisoner> prisoners = new ArrayList<>();

BufferedReader in;
try {
    in = new BufferedReader(new FileReader(filename));
    String line;


    int i=0;
    while((line = in.readLine()) != null)
    {
        if(line.compareToIgnoreCase("white")==0){       
                prisoners.add(new Prisoner(true, (i++%2==1)));
            }else{
                prisoners.add(new Prisoner(false, (i%2==1)));
            }
        }
        in.close();
    } catch (IOException e) {
        e.printStackTrace();
    }

    return prisoners;
}

}

final class Prisoner {

/**

• The color of the prisoner's hat. */ private boolean white;

/** * True if the number of white hats the prisoner sees in front of him is odd */ private boolean oddAhead;

Prisoner(boolean white, boolean oddAhead){ this.white = white; this.oddAhead = oddAhead; }

/** * {(first XOR previousOdd) XOR oddAhead} * is equal to {(first + previousOdd + oddAhead)%2} * assuming true == 1 and false == 0 * * @param previousOdd If the number of passed white hats is Odd then takes true, false otherwise * @param first True if the first prisoner saw odd number of white hats * @return True if the color of the present prisoner is white, false otherwise */ public boolean findColor(boolean previousOdd, boolean first){ return (first^{previousOdd)oddAhead;} }

public boolean getColor(){
    return white;
}

public boolean getOddAhead(){
    return oddAhead;
}

}