[ProjectEuler] ID035 Circular Primes (Overkill Edition)

package atomicdiamond.euler.id26_50;

import static vrabus.euler.common.CommonUtilities.isPrime;

import java.util.ArrayList;

/**
 * @see <a href="https://projecteuler.net/problem=35">Webpage</a>
 */
public class ID035_CircularPrimes {
    static int target = 1_000_000;
    static boolean[] cPrimes = new boolean[target + 1];

    public static void main(String[] args) {

        // take advantage of what is already given
        int[] given = { 2, 3, 5, 7, 11, 13, 17, 31, 37, 71, 73, 79, 97 };

        long count = 0;

        for (int i : given) {
            cPrimes[i] = true;
        }

        // Actualy logic starts here
        for (int ret = 0; ;) {
            ret = Generator.getNext();
            if (ret > target) {
                break;
            }
            doCyclic(String.valueOf(ret));
        }

        for (int i = 0; i < cPrimes.length; i++) {
            if (cPrimes[i]) {
                System.out.println(i);
                count++;
            }

        }


        System.out.println("count = " + count);

    }

    private static void doCyclic(String num) {
        ArrayList<Integer> n = new ArrayList<>(num.length());
        ArrayList<Integer> cycles = new ArrayList<>(num.length());

        for (int i = 0; i < num.length(); i++) {
            n.add(Integer.parseInt(num.substring(i, i+1)));
        }

        int size = n.size();

        boolean isCPrime = true;
        for (int i = 0; i < size; i++) {
            cycles.add(convertArrayToNum(n));
            isCPrime = isCPrime && isPrime(cycles.get(cycles.size()-1));
            doCycle(n, size);
            if (convertArrayToNum(n) > target) {
                return;
            }
        }

        if (isCPrime) {
            for (int i = 0; i < size; i++) {
                try {
                    cPrimes[cycles.get(i)] = true;
                } catch (ArrayIndexOutOfBoundsException e) {
                }
            }

        }

    }

    private static void doCycle(ArrayList<Integer> n, int size) {
        int first = n.get(0);
        for (int j = 0; j < size-1; j++) {
            n.set(j, n.get(j+1));
        }
        n.set(n.size()-1, first);
    }



    private static int convertArrayToNum(ArrayList<Integer> num) {
        int ret = 0;
        for (int i = 0; i < num.size(); i++) {
            ret += (num.get(i) * Math.pow(10, i));
        }
        return ret;
    }
    /**
     * A circular prime bigger than 9 must end in one of four digits: { 1, 3, 7, 9 }. That's why this even exists
     */
    static class Generator {

        // the number is read backwards
        private static ArrayList<SubGenerator> num = new ArrayList<>();
        private static boolean isFirst = true;

        static {
            num.add(new SubGenerator());
            num.add(new SubGenerator());
            num.add(new SubGenerator());
        }

        public static int getNext() {
            if (!isFirst) {

                for (int i = 0; ; ) {
                    if (i >= num.size()) {
                        num.add(new SubGenerator());
                    }

                    if (num.get(i).getNext() == 1) {
                        i++;
                    } else {
                        break;
                    }
                }

            } else {
                isFirst = false;
            }

//          System.out.println(Arrays.toString(num.toArray()));

            int ret = 0;
            for (int i = 0; i < num.size(); i++) {
                ret += (num.get(i).getCur() * Math.pow(10, i));
            }
            return ret;
        }

        private static class SubGenerator {
            private int cur;

            public SubGenerator() {
                this(1);
            }

            public SubGenerator(int start) {
                cur = start;
            }

            public int getCur() {
                return cur;
            }

            int getNext() {
                if (cur >= 9) {
                    cur = -1;
                }

                cur += 2;

                if (cur % 5 == 0) {
                    return getNext();
                }

                return cur;
            }

            @Override
            public String toString() {
                return String.valueOf(cur);
            }
        }

    }

}