Java链表操作代码

/**
 * 
 */
package com.cherish.SwordRefersToOffer;

/**
 * @author acer
 *
 */
public class test_22链表中倒数第k个节点 {

    /**
     * 
     */
    public test_22链表中倒数第k个节点() {
        // TODO 自动生成的构造函数存根
    }
    
    public static class ListNode{
        private    int val;
        ListNode next = null;
        ListNode(int val){
            this.val = val;
            next = null;
        }
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO 自动生成的方法存根
        ListNode head = new ListNode(1);
        //给一个链表赋值
        for(int i = 2;i<10;i++) {
            insertNodeFromTail(head,new ListNode(i));
        }
        printListNode(head);
        System.out.println(FindKthToTail(head,4).val);
        System.out.println(listNodeLength(head));
        System.out.println(deleteFromIndex(head,4));
        printListNode(head);
        System.out.println(listNodeLength(head));
        System.out.println(FindKthToTail(head,4).val);
        

    }
    
    //找到倒数第k个节点
    public static ListNode FindKthToTail(ListNode head,int k) {
        if(head == null||k <= 0) {
            return null;
        }
        ListNode p1 = head;
        ListNode p2 = head;
        for(int i = 1;i<k;i++) {
            if(p1.next != null) {
                p1 = p1.next;
            }else {
                return null;
            }            
        }
        while(p1.next != null) {
            p1 = p1.next;
            p2 = p2.next;
        }
        return p2;
    }
    
    //从头部插入新节点
    public static void insertNodeFromHead(ListNode head,ListNode newNode)
    {
        newNode.next = head;
        head = newNode;
    }
    
    //从尾部插入新节点
    public static void insertNodeFromTail(ListNode head,ListNode newNode)
    {
        if(head == null) {
            head = newNode;
            return;
        }
        ListNode temp = head;//用temp代替head去遍历找到最后一个节点，一定不要用head自己去遍历，不然就找不到链表头了
        while(temp.next != null) { //下一节点不为空
            temp = temp.next;
        }
        temp.next = newNode;//找到最后一个节点后把新节点插入进去
    }
    
    //计算链表的长度
    public static int listNodeLength(ListNode head) {
        if(head ==null) {
            return 0;
        }
        ListNode temp = head;
        int length = 0;
        while(temp.next != null) {
            length++;
            temp = temp.next;            
        }
        return length;
    }
    
    //从特定位置删除链表
    public static boolean deleteFromIndex(ListNode head,int deleteIndex)
    {
        if(head == null || deleteIndex<1) {
            return false;
        }
        if(deleteIndex == 1) {
            head = head.next;
            return true;
        }
        int index = 1;
        ListNode temp = head;
        ListNode deleteNode;
        while(temp.next != null && index < deleteIndex) {
            index++;
            temp = temp.next;
        }
        deleteNode = temp.next;
        temp.next = deleteNode.next;
        return true;
    }
    
    //按顺序输出链表
    public static void printListNode(ListNode head)
    {
        ListNode temp = head;
        while(temp.next != null)
        {
            System.out.print(temp.val);
            System.out.print("\t");
            temp = temp.next;
        }
        System.out.println();
    }
    

}