[LeetCode] 25. Reverse Nodes in k-Group java__java

    /**25. Reverse Nodes in k-Group      * @param head     * @param k     * @return 以k為單位交換節點     */    public ListNode reverseKGroup(ListNode head, int k) {        if (head == null || k == 0 || k == 1) {            return head;        }        ListNode ret = new ListNode(-1);        ListNode add = ret;        ListNode slow = head;        ListNode fast = head;        while (fast != null) {            int i= 0;            for (; i < k && fast != null; i++) {                fast = fast.next;            }            if (i == k) {                ListNode begin = slow;                while (slow != fast) {                    ListNode next = slow.next;                    slow.next = add.next;                    add.next = slow;                    slow = next;                }                add = begin;            } else {                add.next = slow;            }            slow = fast;        }        return ret.next;    }

slow-fast為要逆序的部門，一次添加到ret後，用add執行添加