单链表的操作（删除和排序）

数据结构与算法

class ListNode {
    int val;
    ListNode next;
    public ListNode(int val) {
        this.val = val;
    }
}
class MyLinkedList {
    private ListNode head;
    public void add(ListNode node) {
        if (length() == 0) {
            head = node;
        } else {
            ListNode p = head;
            while (p.next != null) {
                p = p.next;
            }
            p.next = node;
        }
    }
// 删除
    public boolean delete(int index) {
        ListNode p = head;
        if (length() == 0 || length() < index + 1) {
            return false;
        }
        int counter = 0;
        if (index == 0) {
            head = p.next;
        }
        //这里一定要熟练，主要是找前一个
        while (p.next != null) {
            if (counter == index - 1) {
                if (p.next.next != null) {
                    p.next = p.next.next;
                } else {
                    p.next = null;
                }
                break;
            } else {
                p = p.next;
                counter++;
            }
        }
        return true;
    }
    public int length() {
        int counter = 0;
        ListNode p = head;
        while (p != null) {
            counter++;
            p = p.next;
        }
        return counter;
    }
    //选择排序
    public ListNode sort() {
        ListNode p = head;
        ListNode q;
        while (p.next != null) {
            q = p.next;
            while (q != null) {
                if (p.val < q.val) {
                    int temp = p.val;
                    p.val = q.val;
                    q.val = temp;
                }
                q = q.next;
            }
            p = p.next;
        }
        return head;
    }
    public void print() {
        ListNode p = head;
        while (p != null) {
            System.out.print(p.val + "  ");
            p = p.next;
        }
    }
}
public class Test {
    public static void main(String[] args) {
        MyLinkedList list = new MyLinkedList();
        for (int i = 0; i < 10; i++) {
            list.add(new ListNode(i));
        }
        list.print();
        System.out.println();
        System.out.println("链表长度：" + list.length());
        if (list.delete(2)) {
            System.out.println("删除成功");
        }
        list.print();
        System.out.println();
        System.out.println("链表长度：" + list.length());
        list.sort();
        list.print();
        System.out.println();
        System.out.println("链表长度：" + list.length());
    }
}