两个递增的链表合并
1 ListNode f12( LstNode head1,LstNode head2){ 2 if(head1==null ) return head2; 3 if( head1== null ) return head1; 4 5 LstNode newhead =null; 6 7 if( head1.value<head2.value) 8 { 9 newhead =head2; 10 newhead.next = f12 ( head2.next ,head1 ); 11 } 12 else { 13 newhead =head1 14 newhead.next = f12 ( head1.next ,head2 ); 15 } 16 17 return newhead; 18 }