2095. delete the intermediate node of the linked list

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subject ：2095. Delete the intermediate node of the linked list
describe ： Give you a list of the head node head . Delete Linked list Intermediate nodes , And return the head node of the modified linked list head .

The length is n The middle node of the linked list is... From the beginning ⌊n / 2⌋ Nodes （ Subscript from 0 Start ）, among ⌊x⌋ Is less than or equal to x Maximum integer for .

about n = 1、2、3、4 and 5 The situation of , The subscripts of the intermediate nodes are 0、1、1、2 and 2 .

Their thinking

1、 Double pointer ;
2、 Note the special case of only one node ;

Source code ##

class Solution {
    
public:
    ListNode* deleteMiddle(ListNode* head) {
    
        ListNode *slow = head, *fast = head;
        if (fast->next == nullptr) return nullptr;
        while (1) {
    
            if (fast->next == nullptr) {
    
                slow->val = slow->next->val;
                slow->next = slow->next->next;
                break;
            } else if (fast->next != nullptr && fast->next->next == nullptr) {
    
                slow->next = slow->next->next;
                break;
            }
            fast = fast->next->next;
            slow = slow->next;
        }
        return head;
    }
};