[ADS] Playful List

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

class DLLNode<E> {
    protected E element;
    protected DLLNode<E> pred, succ;

    public DLLNode(E elem, DLLNode<E> pred, DLLNode<E> succ) {
        this.element = elem;
        this.pred = pred;
        this.succ = succ;
    }

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


class DLL<E extends Comparable<E>> {
    private DLLNode<E> first, last;

    public DLL() {
        // Construct an empty SLL
        this.first = null;
        this.last = null;
    }

    public void deleteList() {
        first = null;
        last = null;
    }

    public int length() {
        int ret;
        if (first != null) {
            DLLNode<E> tmp = first;
            ret = 1;
            while (tmp.succ != null) {
                tmp = tmp.succ;
                ret++;
            }
            return ret;
        } else
            return 0;

    }

    public DLLNode<E> find(E o) {
        if (first != null) {
            DLLNode<E> tmp = first;
            while (tmp.element != o && tmp.succ != null)
                tmp = tmp.succ;
            if (tmp.element == o) {
                return tmp;
            } else {
                System.out.println("Elementot ne postoi vo listata");
            }
        } else {
            System.out.println("Listata e prazna");
        }
        return first;
    }

    public void insertFirst(E o) {
        DLLNode<E> ins = new DLLNode<E>(o, null, first);
        if (first == null)
            last = ins;
        else
            first.pred = ins;
        first = ins;
    }

    public void insertLast(E o) {
        if (first == null)
            insertFirst(o);
        else {
            DLLNode<E> ins = new DLLNode<E>(o, last, null);
            last.succ = ins;
            last = ins;
        }
    }

    public void insertAfter(E o, DLLNode<E> after) {
        if (after == last) {
            insertLast(o);
            return;
        }
        DLLNode<E> ins = new DLLNode<E>(o, after, after.succ);
        after.succ.pred = ins;
        after.succ = ins;
    }

    public void insertBefore(E o, DLLNode<E> before) {
        if (before == first) {
            insertFirst(o);
            return;
        }
        DLLNode<E> ins = new DLLNode<E>(o, before.pred, before);
        before.pred.succ = ins;
        before.pred = ins;
    }

    public E deleteFirst() {
        if (first != null) {
            DLLNode<E> tmp = first;
            first = first.succ;
            if (first != null) first.pred = null;
            if (first == null)
                last = null;
            return tmp.element;
        } else
            return null;
    }

    public E deleteLast() {
        if (first != null) {
            if (first.succ == null)
                return deleteFirst();
            else {
                DLLNode<E> tmp = last;
                last = last.pred;
                last.succ = null;
                return tmp.element;
            }
        }
        // else throw Exception
        return null;
    }

    public E delete(DLLNode<E> node) {
        if (node == first) {
            deleteFirst();
            return node.element;
        }
        if (node == last) {
            deleteLast();
            return node.element;
        }
        node.pred.succ = node.succ;
        node.succ.pred = node.pred;
        return node.element;

    }

    @Override
    public String toString() {
        String ret = new String();
        if (first != null) {
            DLLNode<E> tmp = first;
            ret += tmp + "<->";
            while (tmp.succ != null) {
                tmp = tmp.succ;
                ret += tmp + "<->";
            }
        } else
            ret = "Prazna lista!!!";
        return ret;
    }

    public String toStringR() {
        String ret = new String();
        if (last != null) {
            DLLNode<E> tmp = last;
            ret += tmp + "<->";
            while (tmp.pred != null) {
                tmp = tmp.pred;
                ret += tmp + "<->";
            }
        } else
            ret = "Prazna lista!!!";
        return ret;
    }

    public DLLNode<E> getFirst() {
        return first;
    }

    public DLLNode<E> getLast() {

        return last;
    }

    public void deleteDuplicates() {
        /*if (first != null) {
            DLLNode<E> tmp = first, tmp2 = tmp.succ;
            while (tmp.succ != null) {
                while (tmp2 != null) {
                    if (tmp.element.compareTo(tmp2.element) == 0) {
                        tmp2 = tmp2.succ;
                        this.delete(tmp2.pred);
                    } else
                        tmp2 = tmp2.succ;
                }
                tmp = tmp.succ;
                tmp2 = tmp.succ;
            }
        } else
            return;*/


        if (first != null) {
            DLLNode<E> current = first;
            DLLNode<E> following = first.succ;
            while (current.succ != null) {
                while (following != null) {
                    if (current.element.equals(following.element)) {
                        following = following.succ;
                        delete(following.pred);
                    } else {
                        following = following.succ;
                    }
                }
                current = current.succ;
                following = current.succ;
            }
        }
        return;
    }


}

public class WeightedSum {

/*
Sample input
10 3
1 9 2 3 6 1 3 2 1 3

Sample output
37
*/

    /* 1⋅првиотброј+2⋅вториотброј+…+K⋅K−тиотброј */
    static int solve(int numbers[], int len, int choose) {
        int matrix[][] = new int[len][choose];
        int result = 0;

        for (int i = 1; i < len; i++) {
            for (int j = 1; j < choose; j++) {
                for (int k = 0; k < i; k++) {
                    int abs = j * numbers[k];
                    if (matrix[i][j] < matrix[k][j - 1] + abs) {
                        matrix[i][j] = matrix[k][j - 1] + abs;
                    }
                }
                if (matrix[i][j] > result) {
                    result = matrix[i][j];
                }
            }
        }

        for (int i = 0; i < matrix.length; i++) {
            for (int j = 0; j < matrix[0].length; j++) {
                System.out.print(matrix[i][j] + " ");
            }
            System.out.println();
        }


        return result;
    }

    public static void swap(final int a[], final int i, final int j) {
        final int temp = a[i];
        a[i] = a[j];
        a[j] = temp;
    }

    public static void printArray(final int a[]) {
        for (int i = 0; i < a.length; i++) {
            System.out.print(a[i] + " ");
        }
        System.out.println();
    }

    public static void printArray(final String a[]) {
        for (int i = 0; i < a.length; i++) {
            System.out.print(a[i] + "");
        }
        System.out.println();
    }

    public static void main(String[] args) throws Exception {

        /*BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine());
        int N = Integer.parseInt(st.nextToken());
        int K = Integer.parseInt(st.nextToken());

        int numbers[] = new int[N];

        st = new StringTokenizer(br.readLine());
        for (int i = 0; i < N; i++) {
            numbers[i] = Integer.parseInt(st.nextToken());
        }
        int res = solve(numbers, N, K);
        System.out.println(res);
        br.close();
        */

        /*int digits[] = new int[10];
        int size = 7;
        for (int i = 0; i < size; i++) {
            digits[i] = i;
        }
        printArray(digits);

        for (int i = size; i > 0; i--) {
            swap(digits, i, 2 + i);
        }
        printArray(digits);

        int index = 3;
        int elemsToMove = size - index + 1;
        System.arraycopy(digits, index, digits, index+1, elemsToMove);
        printArray(digits);*/

        /*
        // Deletes Duplicates
        DLL<Integer> list = new DLL<>();
        for (int i = 0; i < 5; i++) {
            list.insertLast(i);
        }
        for (int i = 1; i < 6; i++) {
            list.insertLast(i);
        }
        System.out.println(list);

        list.deleteDuplicates();

        System.out.println(list);*/

        DLL<Character> list = new DLL<>();
        String letters = "abcdefghij";
        char characters[] = letters.toCharArray();

        for (int i = 0; i < characters.length; i++) {
            list.insertLast((Character) characters[i]);
        }
        System.out.println(list);

        // From the beginning
        //DLLNode first = list.getFirst();
        //DLLNode last = list.getLast();
        /*for (DLLNode first = list.getFirst();  first != null; first = first.succ){
            list.delete(first.succ);
        }
        System.out.println(list);*/
        System.out.println(list.length());
        while (list.length() != 1) {
            DLLNode first = list.getFirst();
            //System.out.println("First Element: " + first.element);
            while (first != null) {
                if (first.succ != null) {
                    list.delete(first.succ);
                }
                first = first.succ;
            }
            System.out.println("From Front");
            System.out.println(list);

            DLLNode last = list.getLast();
            //System.out.println("Last Element: " + last.element);
            while (last != null) {
                //System.out.println("While Last Element: " + last.element);
                if (last.pred != null) {
                    list.delete(last.pred);
                }
                last = last.pred;

            }
            System.out.println("From Back");
            System.out.println(list);
        }

        System.out.println("\nFINAL\n");
        System.out.println(list);
    }

}