algo/java/06_linkedlist/SinglyLinkedList.java

package linkedlist;

/**
 * 1）单链表的插入、删除、查找操作；
 * 2）链表中存储的是int类型的数据；
 *
 * Author：Zheng
 */
public class SinglyLinkedList {

    private Node head = null;

    public Node findByValue(int value) {
        Node p = head;
        while (p != null && p.data != value) {
            p = p.next;
        }

        return p;
    }

    public Node findByIndex(int index) {
        Node p = head;
        int pos = 0;
        while (p != null && pos != index) {
            p = p.next;
            ++pos;
        }

        return p;
    }

    //无头结点
    //表头部插入
    //这种操作将于输入的顺序相反，逆序
    public void insertToHead(int value) {
        Node newNode = new Node(value, null);
        insertToHead(newNode);
    }

    public void insertToHead(Node newNode) {
        if (head == null) {
            head = newNode;
        } else {
            newNode.next = head;
            head = newNode;
        }
    }

    //顺序插入
    //链表尾部插入
    public void insertTail(int value){

        Node newNode = new Node(value, null);
        //空链表，可以插入新节点作为head，也可以不操作
        if (head == null){
            head = newNode;

        }else{
            Node q = head;
            while(q.next != null){
                q = q.next;
            }
            newNode.next = q.next;
            q.next = newNode;
        }
    }
    public void insertAfter(Node p, int value) {
        Node newNode = new Node(value, null);
        insertAfter(p, newNode);
    }

    public void insertAfter(Node p, Node newNode) {
        if (p == null) return;

        newNode.next = p.next;
        p.next = newNode;
    }

    public void insertBefore(Node p, int value) {
        Node newNode = new Node(value, null);
        insertBefore(p, newNode);
    }

    public void insertBefore(Node p, Node newNode) {
        if (p == null) return;
        if (head == p) {
            insertToHead(newNode);
            return;
        }

        Node q = head;
        while (q != null && q.next != p) {
            q = q.next;
        }

        if (q == null) {
            return;
        }

        newNode.next = p;
        q.next = newNode;

    }

    public void deleteByNode(Node p) {
        if (p == null || head == null) return;

        if (p == head) {
            head = head.next;
            return;
        }

        Node q = head;
        while (q != null && q.next != p) {
            q = q.next;
        }

        if (q == null) {
            return;
        }

        q.next = q.next.next;
    }

    public void deleteByValue(int value) {
        if (head == null) return;

        Node p = head;
        Node q = null;
        while (p != null && p.data != value) {
            q = p;
            p = p.next;
        }

        if (p == null) return;

        if (q == null) {
            head = head.next;
        } else {
            q.next = q.next.next;
        }

        // 可重复删除指定value的代码
        /*
           if (head != null && head.data == value) {
           head = head.next;
           }

           Node pNode = head;
           while (pNode != null) {
           if (pNode.next.data == data) {
           pNode.next = pNode.next.next;
           continue;
           }
           pNode = pNode.next;
           }
         */
    }

    public void printAll() {
        Node p = head;
        while (p != null) {
            System.out.print(p.data + " ");
            p = p.next;
        }
        System.out.println();
    }

    //判断true or false
    public boolean TFResult(Node left, Node right){
        Node l = left;
        Node r = right;

        System.out.println("left_:"+l.data);
        System.out.println("right_:"+r.data);
        while(l != null && r != null){
           if (l.data == r.data){
               l = l.next;
               r = r.next;
               continue;
           }else{
               break;
           }

        }

        System.out.println("什么结果");
        if (l==null && r==null){
           System.out.println("什么结果");
           return true;
        }else{
           return false;
        }
    }
    //　判断是否为回文 

    public boolean palindrome(){
       if (head == null){
           return false;
       }else{
           System.out.println("开始执行找到中间节点");
           Node p = head;
           Node q = head;
           if (p.next == null){
               System.out.println("只有一个元素");
               return true;
           }
           while( q.next != null && q.next.next != null){
               p = p.next;
               q = q.next.next;

           }

           System.out.println("中间节点" + p.data);
           System.out.println("开始执行奇数节点的回文判断");
           Node leftLink = null;
           Node rightLink = null;
           if(q.next == null){
               //　p 一定为整个链表的中点，且节点数目为奇数
               rightLink = p.next;
               leftLink = inverseLinkList(p).next;
               System.out.println("左边第一个节点"+leftLink.data);
               System.out.println("右边第一个节点"+rightLink.data);

           }else{
               //p q　均为中点
               rightLink = p.next;
               leftLink = inverseLinkList(p);
           }
           return TFResult(leftLink, rightLink);

       }
    }

    //带结点的链表翻转
    public Node inverseLinkList_head(Node p){
        //　Head　为新建的一个头结点
        Node Head = new Node(9999,null);
        // p　为原来整个链表的头结点,现在Head指向　整个链表
        Head.next = p;
        /*
        带头结点的链表翻转等价于
        从第二个元素开始重新头插法建立链表
        */
        Node Cur = p.next;
        p.next = null;
        Node next = null;

        while(Cur != null){
            next = Cur.next;
            Cur.next = Head.next;
            Head.next = Cur;
            System.out.println("first " + Head.data);

            Cur = next;
        }

        //　返回左半部分的中点之前的那个节点
        //　从此处开始同步像两边比较
        return Head;

    }

    //无头结点的链表翻转
    public Node inverseLinkList(Node p){

        Node pre = null;
        Node r = head;
        System.out.println("z---" + r.data);
        Node next= null;
        while(r !=p){
            next = r.next;

            r.next = pre;
            pre = r;
            r = next;
        }

        r.next = pre;
        //　返回左半部分的中点之前的那个节点
        //　从此处开始同步像两边比较
        return r;

    }
    
    public static Node createNode(int value) {
        return new Node(value, null);
    }

    public static class Node {
        private int data;
        private Node next;

        public Node(int data, Node next) {
            this.data = data;
            this.next = next;
        }

        public int getData() {
            return data;
        }
    }
    public static void main(String[]args){

        SinglyLinkedList link = new SinglyLinkedList(); 
        System.out.println("hello");
        //int data[] = {1};
        //int data[] = {1,2};
        //int data[] = {1,2,3,1};
        //int data[] = {1,2,5};
        //int data[] = {1,2,2,1};
       // int data[] = {1,2,5,2,1};
        int data[] = {1,2,5,3,1};

        for(int i =0; i < data.length; i++){
            //link.insertToHead(data[i]);
            link.insertTail(data[i]);
        }
       // link.printAll();
       // Node p = link.inverseLinkList_head(link.head);
       // while(p != null){
       //     System.out.println("aa"+p.data);
       //     p = p.next;
       // }

        System.out.println("打印原始:");
        link.printAll();
        if (link.palindrome()){
            System.out.println("回文");
        }else{
            System.out.println("不是回文");
        }
    }

}