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;    }