21.Merge Two Sorted Lists (E)

1.Description(Easy)

Merge two sorted (ascending) linked lists and return it as a new sorted list. The new sorted list should be made by splicing together the nodes of the two lists and sorted in ascending order.

Example

Given1->3->8->11->15->null,2->null, return1->2->3->8->11->15->null.

2.Code

用到了Dummy Node

public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        ListNode dummy=new ListNode(0);
        ListNode lastNode=dummy;

        while(l1!=null && l2!=null){
            if(l1.val<l2.val){
                lastNode.next=l1;
                l1=l1.next;
            }else{
                lastNode.next=l2;
                l2=l2.next;
            }
            lastNode=lastNode.next;
        }
        if(l1!=null){
            lastNode.next=l1;
        }
        if(l2!=null){
            lastNode.next=l2;
        }
        return dummy.next;
    }