[АПС] колоквиум 2018

/**Парни разменливи елементи на дадена поврзана листа
Со оглед на листата со поединечно поврзана вредност, напишете функција за да ги замените елементите.
На пример, ако поврзаната листа е 1-> 2-> 3-> 4-> 5 тогаш функцијата треба да ја смени на 2-> 1-> 4-> 3-> 5,  и ако поврзаната листа е  1-> 2-> 3-> 4-> 5-> 6 тогаш функцијата треба да ја промени на 2-> 1-> 4-> 3-> 6-> 5.
*/


//CODE



import java.util.Scanner;

class SLLNode<E> {
    protected E element;
    protected SLLNode<E> succ;

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

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

class SLL<E> {
    private SLLNode<E> first;

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

    public void deleteList() {
        first = null;
    }

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

    }

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

    public void insertFirst(E o) {
        SLLNode<E> ins = new SLLNode<E>(o, first);
        first = ins;
    }

    public void insertAfter(E o, SLLNode<E> node) {
        if (node != null) {
            SLLNode<E> ins = new SLLNode<E>(o, node.succ);
            node.succ = ins;
        } else {
            System.out.println("Dadenot jazol e null");
        }
    }

    public void insertBefore(E o, SLLNode<E> before) {

        if (first != null) {
            SLLNode<E> tmp = first;
            if (first == before) {
                this.insertFirst(o);
                return;
            }
            while (tmp.succ != before)
                tmp = tmp.succ;
            if (tmp.succ == before) {
                SLLNode<E> ins = new SLLNode<E>(o, before);
                tmp.succ = ins;
            } else {
                System.out.println("Elementot ne postoi vo listata");
            }
        } else {
            System.out.println("Listata e prazna");
        }
    }

    public void insertLast(E o) {
        if (first != null) {
            SLLNode<E> tmp = first;
            while (tmp.succ != null)
                tmp = tmp.succ;
            SLLNode<E> ins = new SLLNode<E>(o, null);
            tmp.succ = ins;
        } else {
            insertFirst(o);
        }
    }

    public E deleteFirst() {
        if (first != null) {
            SLLNode<E> tmp = first;
            first = first.succ;
            return tmp.element;
        } else {
            System.out.println("Listata e prazna");
            return null;
        }
    }

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

    }

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

    public SLLNode<E> find(E o) {
        if (first != null) {
            SLLNode<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 class Kolokvium2018 {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        SLL<Integer> list = new SLL<Integer>();
        int n = input.nextInt();

        for (int i = 0; i < n; i++)
            list.insertLast(input.nextInt());

        swap(list, n);
        input.close();
    }

    private static void swap(SLL<Integer> list, int n) {
        SLLNode<Integer> current = list.getFirst();
        SLLNode<Integer> next = current.succ;
        if (n % 2 == 0) {
            while (n > 1) {
                list.insertLast(next.element);
                list.delete(next);
                list.insertLast(current.element);
                list.delete(current);
                current = next.succ;
                next = next.succ.succ;
                n -= 2;
            }
        } else {
            while (n > 1) {
                list.insertLast(next.element);
                list.delete(next);
                list.insertLast(current.element);
                list.delete(current);
                current = next.succ;
                --n;
                if (n < 1)
                    break;
                next = next.succ.succ;
                --n;
            }
            list.insertLast(current.element);
            list.delete(current);
        }

        System.out.println(list);
    }
}