Remove Nth Node From End of List

Given a linked list, remove the nth node from the end of list and return its head.

For example,

   Given linked list: 1->2->3->4->5, and n = 2.

   After removing the second node from the end, the linked list becomes 1->2->3->5

    ListNode *removeNthFromEnd(ListNode *head, int n){
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        ListNode *fast = head, *slow = head, *rm = head;
        while (n--){
            fast = fast->next;
        }
        
        if (fast == NULL){
            head =head->next;
            free(rm);
            return head;
        }

        while (fast->next != NULL){
            fast = fast->next;
            slow = slow->next;
        }
        
        rm = slow->next;
        slow->next = rm->next;
        free(rm);
        return head;
    }