Solution.java

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode insertionSortList(ListNode head) {
        if (head == null || head.next == null) {
            return head;
        }
        ListNode dummy = new ListNode(head.val);
        dummy.next = head;
        ListNode pre = dummy, cur = head;
        while (cur != null) {
            if (pre.val <= cur.val) {
                pre = cur;
                cur = cur.next;
                continue;
            }
            ListNode p = dummy;
            while (p.next.val <= cur.val) {
                p = p.next;
            }
            ListNode t = cur.next;
            cur.next = p.next;
            p.next = cur;
            pre.next = t;
            cur = t;
        }
        return dummy.next;
    }
}