package BullsAndCows;

import java.util.HashSet;
import java.util.Iterator;
import java.util.Random;
import java.util.Scanner;
import java.util.Set;

public class BandC {
    public static void main(String[] args) {
        Set<String> possibleNums = generatePossibleNums();
        int steps = 0;
        System.out.println("Hello! I am your computer!nNow think of a number...");
        Scanner reader = new Scanner(System.in);
        while (true) {
            steps++;
            Iterator<String> iter = possibleNums.iterator();
            String AIguess = iter.next();
            System.out.println("My guess is: " + AIguess);
            System.out.print("Number of cows:");
            int numberOfCows = reader.nextInt();
            System.out.print("Number of bulls:");
            int numberOfBulls = reader.nextInt();
            removeWrongNums(new BcCount(numberOfBulls, numberOfCows), AIguess, possibleNums);
            if (numberOfBulls == 4) {
                System.out.println("Guessed in " + steps + " steps");
                break;
            }
        }
        reader.close();
    }

    public static BcCount calcBullandCowCount(String guess, String candidate) {
        BcCount bcCount = new BcCount(0, 0);
        for (int i = 0; i < candidate.length(); i++) {
            if (guess.charAt(i) == candidate.charAt(i)) {
                bcCount.bullCount++;
            } else if (guess.contains(String.valueOf(candidate.charAt(i)))) {
                bcCount.cowCount++;
            }
        }
        return bcCount;
    }

    public static Set<String> generatePossibleNums() {
        Set<String> set = new HashSet<String>();
        for (int i = 1000; i < 10_000; i++) {
            set.add(String.valueOf(i));
        }
        Iterator<String> iter = set.iterator();
        while (iter.hasNext()) {
            String str = iter.next();
            Set<Character> digits = new HashSet<>();
            for (char c : str.toCharArray()) {
                if (digits.contains(c)) {
                    iter.remove();
                    break;
                }
                digits.add(c);
            }
        }
        return set;
    }

    public static void removeWrongNums(BcCount guessBcCount, String guess,
            Set<String> possibleNums) {
        Iterator<String> iter = possibleNums.iterator();
        while (iter.hasNext()) {
            String str = iter.next();
            if (calcBullandCowCount(guess, str).equals(guessBcCount) == false) {
                iter.remove();
            }
        }
    }

}

package BullsAndCows;

public class BcCount {
    public int bullCount = 0;
    public int cowCount = 0;

    public BcCount(int b, int c) {
        bullCount = b;
        cowCount = c;
    }

    public String toString() {
        return bullCount + " " + cowCount;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        BcCount other = (BcCount) obj;
        if (bullCount != other.bullCount)
            return false;
        if (cowCount != other.cowCount)
            return false;
        return true;
    }
}