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/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode deleteMiddle(ListNode head) {
        
        if (head == null) return null;

        ListNode fast = head;
        ListNode slow = head;
        ListNode prev = null; // 刪除節點要知道前一個節點

        while(fast != null && fast.next != null) {
            prev = slow;
            slow = slow.next;
            fast = fast.next.next;
        }
        // slow 指向中間節點，pre 指向slow前一節點
        if (prev != null) {
            prev.next = slow.next;
        } else {
            //是最開頭的點
            head = head.next;
        }
        return head;
    }
}

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function deleteNode(head, target):
    if head is null:
        return head  // 空鏈結，不須刪除
    
    if head.value == target:
        // 删除頭節點
        head = head.next
        return head

    current = head
    while current.next is not null:
        if current.next.value == target:
            current.next = current.next.next  // 删除下一個節點
            return head
        current = current.next

    return head  // 如果未找到目標節點則不變

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function insertNode(head, newNode, position):
    if position == 0:
        // 在鏈結插入節點
        newNode.next = head
        head = newNode
        return head

    current = head
    count = 0
    while current is not null:
        count++
        if count == position:
            // 在當前節點後插入節點
            newNode.next = current.next
            current.next = newNode
            return head
        current = current.next

    // 如果 position 超出鏈結長度，可以選擇插入到尾部
    // 或者根據需要執行其他操作
    return head