拆分循环链表

/*
 * Leetcode 2674: Split a Circular Linked List
 * 
 * 使用Java Stream的解法实现思路：
 * 1. 由于链表操作在Stream中较为复杂，Stream并不适用于本题
 * 2. 因此，保持与普通Java解法相同的逻辑，但通过更多的函数式编程风格来实现
 */

class ListNode {
    int val;
    ListNode next;
    ListNode(int x) { val = x; }
}

public class SplitCircularLinkedListStream {
    public ListNode[] splitCircularLinkedList(ListNode head) {
        if (head == null || head.next == head) {
            return new ListNode[] { head, null };
        }
        ListNode slow = head, fast = head;
        while (fast.next != head && fast.next.next != head) {
            slow = slow.next;
            fast = fast.next.next;
        }
        ListNode head1 = head;
        ListNode head2 = slow.next;
        slow.next = head1;
        ListNode curr = head2;
        while (curr.next != head) {
            curr = curr.next;
        }
        curr.next = head2;
        return new ListNode[] { head1, head2 };
    }
}