876. 链表的中间结点🔖链表

876. 链表的中间结点

• https://leetcode-cn.com/problems/middle-of-the-linked-list/

  问题描述

  

  问题分析

  代码实现

  js

  /**
  * Definition for singly-linked list.
  * function ListNode(val, next) {
  *     this.val = (val===undefined ? 0 : val)
  *     this.next = (next===undefined ? null : next)
  * }
  */
  /**
  * @param {ListNode} head
  * @return {ListNode}
  */
  var middleNode = function(head) {
    let count = 0
    let temp = head
    while(temp) {
        count++
        temp = temp.next
    }
    for(let i = 0; i < (count-1)/2; i++) {
        head = head.next
    }
    return head
  };

  java

  class Solution {
    public ListNode middleNode(ListNode head) {
        if (head.next == null) return head;
        if (head.next.next == null) return head.next;
        ListNode slow = head.next;
        ListNode fast = head.next.next;
        while (fast != null && fast.next != null) {
            slow = slow.next;
            fast = fast.next.next;
            if (fast == null) return slow;
        }
        return slow;
    }
  }