Sort a linked list using insertion sort.
public ListNode InsertionSortList(ListNode head) { if(head == null || head.next == null) return head; ListNode stand = new ListNode(0); ListNode p = head; ListNode s = stand; ListNode nextNode = null; while(p != null) { nextNode = p.next; while(s.next != null && s.next.val <= p.val) { s = s.next; } p.next = s.next; s.next = p; s= stand; p = nextNode; } return stand.next; }