题目0233-单向链表中间节点

题目描述

求单向链表中间的节点值，如果奇数个节点取中间，偶数个取偏右边的那个值。

输入描述

第一行 链表头节点地址 后续输入的节点数 𝑛
后续输入每行表示一个节点，格式 节点地址 节点值 下一个节点地址( -1 表示空指针)
输入保证链表不会出现环，并且可能存在一些节点不属于链表。

输出描述

单向链表中间的节点值

代码实现

import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
import java.lang.Integer;

// 定义链表
class Node {
    int address;
    int number;
    int nextAddress;
    Node next;
    public Node(int address, int number, int nextAddress) {
        this.address = address;
        this.number = number;
        this.nextAddress = nextAddress;
        this.next = null;
    }
}
public class Main {
    public static void main(String[] args) {
        try (Scanner scanner = new Scanner(System.in)) {
            // 头节点地址
            int headAddress = scanner.nextInt();
            // 链表长度
            int count = scanner.nextInt();
            // 存储当前节点
            Map<Integer, Node> map = new HashMap<>();
            for(int i = 0; i < count; i++) {
                int address = scanner.nextInt();
                int number = scanner.nextInt();
                int nextAddress = scanner.nextInt();
                map.put(address, new Node(address, number, nextAddress));
            }
            //查询头节点
            Node head = map.get(headAddress);
            Node current = head;
            //组建链表
            while(current.nextAddress != -1) {
                current.next = map.get(current.nextAddress);
                current = current.next;
            }
            //查询中间节点
            Node fast = head;
            Node slow = head;
            while(fast != null && fast.next != null) {
                fast = fast.next.next;
                slow = slow.next;
            }
            System.out.println(slow.number);
        }
    }
}