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/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode merge(ListNode l1, ListNode l2) {
        ListNode dummy=new ListNode(-1);
        ListNode res=dummy;
        while(l1 != null&& l2 != null){
            if(l1.val<=l2.val){
                res.next=l1;
                res=res.next;
                l1=l1.next;
            }
            else{
                res.next=l2;
                res=res.next;
                l2=l2.next;
            }
        }
        if(l1!=null) res.next=l1;
        else res.next=l2;
        return dummy.next;
    }
}

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* merge(ListNode* l1, ListNode* l2) {
        ListNode* dummy=new ListNode(0);
        ListNode *cur = dummy;
        while(l1!=NULL&&l2!=NULL){
            if(l1->val <l2->val){
                cur->next=l1;
                l1=l1->next;
            }
            else{
                cur->next=l2;
                l2=l2->next;
            }
         cur=cur->next;
    }
    cur -> next = (l1 != NULL ? l1 : l2);
    return dummy->next;
        
    }
};