import java.util.ArrayList;
import java.util.List;
import java.util.Random;

public class Main {

    public static void main(String[] args) {
        Collatz tester = new Collatz();
        /*List<Integer> test = new ArrayList<Integer>();

        System.out.println("wtf");
        for(int i = 1;i < 11000;i++){
            test.add(i);
        }
        for(int x: test){
            System.out.println(x);
        }*/

        tester.fillArray(10);
        tester.iterateCollatz();
        System.out.println("length: " + tester.getLength() + " given by seed " + tester.getLongestSeed());


import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Random;
import javafx.css.Size;

public class Collatz {

    private int longestChain;    // Length of the current longest chain
    private int seed;            // The current seed value, i.e. the value at which the current chain starts
    private int longestSeed;     // Number which generates the longest Collatz sequence
    private List<Integer> array; // ArrayList on which the Collatz sequence operates

    public Collatz() {
        this.longestChain = 1;
        this.array = new ArrayList<>();
        this.seed = 1;
        this.longestSeed = 1;
    }

    // Create an ArrayList with entries 1...n
    public void fillArray(int n) {
        for (int i = (n-1)/2; i < n; i = i++) {
                if(!((n%2 ==0) && (n%3 == 1)))
                this.array.add(i);
        }
    }

    public void iterateCollatz() {
        int i = 1;
        while (this.array.size() > 0) {
            System.out.println("iteration " + i);
            this.setSeed();
            this.runCollatzOperation(this.seed);
            i++;
        }
    }

    public void runCollatzOperation(int n) {
        int m = n;

        int length = 1;
        while (n != 1) {
            if (this.array.contains(n)) {
                this.deleteEntry(n);
            }

            if (n % 2 == 0) {
                n = n / 2;
            }
            else {
                n = 3 * n + 1;
            }
            length++;

        }
        if (length > this.longestChain) {
            this.longestChain = length;
            this.longestSeed = m;
        }

    }
    //Deletes the value n from this.array, if it exists

    public void deleteEntry(int n) {

        this.array.remove(this.array.indexOf(n));

    }

    /*Generate a random number to serve as the seed of the next chain
    from the remaining numbers in this.array */
    public void setSeed() {
        Random generator = new Random();
        int random = generator.nextInt(this.array.size());
        this.seed = this.array.get(random);
    }

    public int getSeed() {
        return this.seed;
    }

    public int getLongestSeed() {
        return this.longestSeed;
    }

    public int getLength() {
        return this.longestChain;
    }

    public int getMax() {
        return Collections.max(this.array);
    }
}