【剑指offer】链表测试

1. 辨析P++，（p++），（++p），++（p），（P--），（--P）
   https://blog.csdn.net/publicstaticfinal/article/details/90005142

2. 剑指offer链表添加，删除元素中传入的pHead为什么要是指向头指针的指针问题?
   https://blog.csdn.net/jmt330/article/details/80166752#commentBox

3. java在方法里new一个对象的生命周期及作用范围
   https://blog.51cto.com/5563447/1286374

package cn.wsw.web.Test;

class ListNode {
    int val;
    ListNode next = null;

    ListNode(int val) {
        this.val = val;
    }
}


public class Solution {

    public static void addNode(ListNode ln) { // ln为形参

        for (int i = 2; i <= 5; i++) {
            ln.next = new ListNode(i);
            ln = ln.next;
        }
    }


    public static void main(String[] args) {

        ListNode ln = new ListNode(1);
        addNode(ln); // ln为实参
        System.out.println(ln.val); // ln仍指向链表头结点

        System.out.println("=====");

        while (ln != null) {
            System.out.println(ln.val);
            ln = ln.next;
        }

    }
}

// 链表测试，语法不熟，多测试一些

package cn.wsw.offer;

import java.util.*;

// 15:31-15:52

class ListNode {
    int val;
    ListNode next = null;
    ListNode (){}
    ListNode(int val) {
        this.val = val;
    }
}

public class Solution {
    public static int FindKthToTail(ListNode head,int k) {
        if(head == null||k<=0){
            return -1;
        }

        ListNode l = head,r = head;
        for(int i=0;i<k-1;i++){
            if(r.next==null){
                return -1;
            }
            r = r.next;
        }
        while(r.next!=null){
            r = r.next;
            l = l.next;
        }
        return l.val;
    }

    public static void main(String[] args) {
        int[] array = {1,2,3,4,5};
        int k = 1;

        ListNode listNode = new ListNode(),t = listNode;
        // ListNode listNOde = new ListNode(array[0]);
        for(int i = 0; i<array.length;i++){
            if(i==0){
                t.val = array[i];
            }else {
                t.next = new ListNode(array[i]);
                t = t.next;
            }
        }
        System.out.println(t.val);
        System.out.println(FindKthToTail(t,k));
    }

}