leetcode-19. 删除链表的倒数第N个节点

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class Solution {
    public ListNode removeNthFromEnd(ListNode head, int n) {
        int count = 0;
        ListNode cur = head;
        while(cur.next != null){
            cur = cur.next;
            count ++;
        }

        cur = head;
        ListNode pre = null;

        int k = count - n + 1;
        while(k > 0){
            pre = cur;
            cur = cur.next;
            k--;
        }

        if(pre != null){
            pre.next = cur.next;
        }else{
            return cur.next;
        }

        return head;
    }
}