Remove Nth Node From End of List, LeetCode, c++/cpp/c

1. 첫 번째 코드

class Solution {
public:
    ListNode* removeNthFromEnd(ListNode* head, int n) {
        int cnt = 1;
        ListNode* from = new ListNode();
        from->next = head;
        ListNode remove = *head;
        while (remove.next) {
            remove = *remove.next;
            cnt++;
        }
        remove = *from;
        for (int i = 0; i < cnt - n - 1; i++) {
            remove = *remove.next;
        }
        ListNode* tmp = remove.next;
        if (tmp->next and n != cnt) tmp->next = tmp->next->next;
        else head = head->next;
        return head;
    }
};

2. 완성한 코드

 

class Solution {
public:
    ListNode* removeNthFromEnd(ListNode* head, int n) {
        ListNode* p = head, *q = head;
        for (int i = 0; i < n; i++) p = p->next;
        if (!p) return head->next;
        while (p->next) {
            p = p->next;
            q = q->next;
        }
        q->next = q->next->next;
        return head;
    }
};