2095-delete-the-middle-node-of-a-linked-list.cpp

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* deleteMiddle(ListNode* head) {
        if(head==NULL){
            return NULL; 
            
        }
        if(head->next==NULL){
            delete head; 
            return NULL; 
            
        }
        ListNode*prev=head;  
        ListNode*slow=head;
        ListNode*fast=head; 
        while(fast!=NULL and fast->next!=NULL){
            if(slow!=head){
prev =prev->next; 
            }
            slow=slow->next; 
            fast=fast->next->next; 
            
        }
        prev->next=slow->next; 
        delete slow; 
        return head;
        
        
        
    }
};