Brooke

一、題目

Given the head of a singly linked list, return the middle node of the linked list.

If there are two middle nodes, return the second middle node.

 

Example 1:

 

 

 

Input: head = [1,2,3,4,5] Output: [3,4,5] Explanation: The middle node of the list is node 3.

Example 2:

 

 

 

Input: head = [1,2,3,4,5,6] Output: [4,5,6] Explanation: Since the list has two middle nodes with values 3 and 4, we return the second one.

 

Constraints:

• The number of nodes in the list is in the range [1, 100].
• 1 <= Node.val <= 100

 

二、程式作法

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     public int val;
 *     public ListNode next;
 *     public ListNode(int val=0, ListNode next=null) {
 *         this.val = val;
 *         this.next = next;
 *     }
 * }
 */
public class Solution
{
    public ListNode MiddleNode(ListNode head)
    {
        int counter = 0;
        ListNode cur = head;

        while (cur != null)
        {
            counter++;
            cur = cur.next;
        }

        for (int i = 0; i < counter / 2 ; i++)
            head = head.next;

        return head;
    }
}

 

三、思路筆記

目的為回傳一 Link List 的中間 Link List 子集。

先要知道整個 Link List 的長度後，才能再去尋找中間點，並將其取出。