单项链表归并排序

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode sortList(ListNode head) {
        if (head==null||head.next==null) return head;
        // ListNode head = head;
        ListNode mid = head;
        ListNode end = head;
        int c = 1;
        while(end.next != null){
            if((c&1) == 0){
            mid = mid.next;
            }

            end = end.next;
            c++;
        }
        ListNode midNext = mid.next;
        mid.next = null;
        end.next = null;
        ListNode list1 = sortList(head);
        ListNode list2 = sortList(midNext);
        return combak(list1,list2);
    }

    public ListNode combak(ListNode lh,ListNode rh){
        ListNode newH = new ListNode(-1);
        ListNode n = newH;
        while(lh != null && rh != null){
            if(lh.val < rh.val){
                newH.next = lh;
                lh = lh.next;
                newH = newH.next;
            }else{
                newH.next = rh;
                rh = rh.next;
                newH = newH.next;
            }
        }
        if(lh != null){
            newH.next = lh;
        }
        if(rh != null){
             newH.next = rh;
        }
        return n.next;
    }

}