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876. Middle of the Linked List

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

SOL：

參考李根逸博士的影片，使用 快慢指針 的方法來解決。

【C 語言的 LeetCode 30 天挑戰】第八天 (Middle of the Linked List)

需要注意的是，->next前面的東西不能為空，否則編譯會有問題。

原本這三者都應該要確認非空：

但因為 fast 一定走的比 slow 還快，所以只要 fast 非空，則 slow 也非空，故 slow!=NULL 可以拿掉。

python 解法參考：[LeetCode] 876. Middle of the Linked List