數據結構與算法（四）鏈表（三）- 雙向鏈表

public class DoublyLinkedList {
    @Test
    public void test() {
        Log.e("DoublyLinkedList", "000000000000000000000000000000000000000000000");
        DoublyLinkedList doublyLinkedList = new DoublyLinkedList();
        doublyLinkedList.add(12);
        doublyLinkedList.add(123);
        doublyLinkedList.add(1234);
        doublyLinkedList.add(12345);

        doublyLinkedList.show();
        Log.e("DoublyLinkedList", "000000000000000000000000000000000000000000000");
        doublyLinkedList.delete(5);
        doublyLinkedList.delete(0);
        doublyLinkedList.delete(2);
        doublyLinkedList.show();
        Log.e("DoublyLinkedList", "000000000000000000000000000000000000000000000");
    }

    class Node {
        Node pre = null;
        Node next = null;
        int data;

        Node(int data) {
            this.data = data;
        }
    }

    Node head = null;

    public void add(int data) {
        Node temp = new Node(data);
        if (head == null) {
            head = temp;
            return;
        }

        Node current = head;
        while (current.next != null) {
            current = current.next;
        }
        current.next = temp;
        temp.pre = current;
    }

    public void delete(int index) {
        if (head == null) {
            Log.e("DoublyLinkedList", "現在是空鏈表");
            return;
        }
        Node current = head;
        for (int i = 0; i < index; i++) {
            //current就是要刪除的結點
            current = current.next;
            if (current == null) {
                Log.e("DoublyLinkedList", "鏈表沒有這麼大");
                return;
            }
        }
        //current是頭結點的情況
        if (current.pre == null) {
            head = current.next;
            return;
        }
        //current是最後一個結點的情況
        if (current.next == null) {
            current.pre.next = null;
            return;
        }
        current.pre.next = current.next;
        current.next.pre = current.pre;

    }

    public void show() {
        Node current = head;
        int count = 0;
        if (current == null) {
            Log.e("DoublyLinkedList", "鏈表還是空的哦");
            return;
        }
        while (current != null) {
            Log.e("DoublyLinkedList", "下標是" + count + "的結點值是：" + current.data);
            current = current.next;
            count++;
        }
    }
}