Interview Road (29)-merge two sorted lists (recursive and non-recursive)

List of classes:

class ListNode{        int key;        ListNodenext;    }

Ideas:

• This and the array are different, do not need to use a double pointer, from the back to come

Code: Recursive

publicmerge(ListNode head1,ListNode head2){        ifnull){            return head2;        }elseifnull){            return head1;        }        null;        if(head1.key < head2.key){            node =head1;            node.next = merge(head1.next,head2);        }else{            node = head2;            node.next = merge(head1,head2.next);        }        return node;    }

Non-recursive

 PublicListNode merge (ListNode Head1,listnode head2) {if(Head1 = =NULL) {return head2; }Else if(Head2 = =NULL) {return head1; } listnode node =NULL;if(Head1.key < Head2.key)            {node = Head1; Head1 = Head1.Next; }Else{node = head2; Head2 = head2.Next; } while(Head1! =NULL&& head2! =NULL){if(Head1.key < Head2.key) {node.Next= Head1; Head1 = Head1.Next; }Else{node.Next= Head2; Head2 = head2.Next; }        }if(Head1 = =NULL) {node = head2; }if(Head2 = =NULL) {node = Head1;    } return node; }

Interview Road (29)-merge two sorted lists (recursive and non-recursive)