[LeetCode] 148. Sort List java__leetcode

    /**148. Sort List      * @param head     * @return O(nlogn)給鏈表排序     */    public ListNode sortList(ListNode head) {        if (head == null || head.next == null)            return head;        ListNode slow = head;        ListNode fast = head;        ListNode pre = head;        while (fast != null && fast.next != null) {            pre = slow;            slow = slow.next;            fast = fast.next.next;        }        pre.next = null;        head = sortList(head);        slow = sortList(slow);        return mergeTwoLists(slow, head);       }

//能夠有O(n lgn)時間複雜度的演算法為，快速排序，堆排序，歸併排序
//根據複雜度想到應該用merge sort方法
//beats 85.60%

利用slow和fast指標找到中點，之後將頭和中間節點進行排序，將排序好的鏈表合并