19. Remove Nth Node From End of List

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class Solution {
    public ListNode removeNthFromEnd(ListNode head, int n) {
        ListNode dummyHead = new ListNode(-1, head);

        // d *
        //   f
        // s

        // d * *
        //     f
        //   s

        ListNode fast = dummyHead, slow = dummyHead;
        for (int i = 0; i < n; i++) {
            fast = fast.next;
        }
        while (fast.next != null) {
            fast = fast.next;
            slow = slow.next;
        }

        slow.next = slow.next.next;
        return dummyHead.next;
    }
}

References

19. Remove Nth Node From End of List
剑指 Offer II 021. 删除链表的倒数第 n 个结点