24.从单向链表中删除指定值的节点

题目描述

输入一个单向链表和一个节点的值，从单向链表中删除等于该值的节点，删除后如果链表中无节点则返回空指针。

链表结点定义如下：

struct ListNode

{

      int       m_nKey;

      ListNode* m_pNext;

};

详细描述：

本题为考察链表的插入和删除知识。

链表的值不能重复

构造过程，例如

1 -> 2

3 -> 2

5 -> 1

4 -> 5

7 -> 2

最后的链表的顺序为 2 7 3 1 5 4 

删除 结点 2 

则结果为 7 3 1 5 4 

import java.util.Scanner;
import java.util.Stack;
 
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while(in.hasNext())
        {
            //输入节点数
            int nodeNum = in.nextInt();
            //输入头节点的值
            int headVal = in.nextInt();
            //构造头节点
            Node pHead = new Node(headVal);
            for(int i = 0;i < nodeNum - 1;i ++)
            {
                //插入节点值
                int nextVal = in.nextInt();
                //前一节点值
                int preVal = in.nextInt();
                //插入节点
                insert(pHead,preVal,nextVal);
            }
            int deleteVal = in.nextInt();
            pHead = removeNode(pHead, deleteVal);
            while(pHead.next != null)
            {
                System.out.print(pHead.val + " ");
                pHead = pHead.next;
            }
            System.out.println(pHead.val + " ");
        }
    }
    /*
     参数 pHead 头节点
     preVal 上一节点值
     nextVal 插入节点值
    */
    public static void insert(Node pHead,int preVal,int nextVal)
    {
        Node pNext = new Node(nextVal);
        Node pCurrent = pHead;
        while(pCurrent != null)
        {
            if(pCurrent.val == preVal)
            {
                pNext.next = pCurrent.next;
                pCurrent.next = pNext;
                break;
            }
            pCurrent = pCurrent.next;
        }
    }
    public static Node removeNode(Node pHead,int val)
    {
        Stack<Node> stack = new Stack<Node>();
Node preNode = pHead;
        while(pHead != null)
        {
            if(pHead.val != val)
            {
                stack.push(pHead);

            }
            pHead = pHead.next;
        }
        while(!stack.isEmpty())
        {
            stack.peek().next = pHead;
            pHead = stack.pop();
        }
        return pHead;
    }
}
class Node
{
    public int val;
    public Node next;
    public Node(int val)
    {
        this.val = val;
    }
}