class Solution {
public:
    ListNode* Merge(ListNode* pHead1, ListNode* pHead2) {
        ListNode* dummy = new ListNode(-1);
        ListNode* cur = dummy;
        while(pHead1 && pHead2){
            if (pHead1->val <= pHead2->val){
                cur->next = pHead1;
                pHead1 = pHead1->next;
            }
            else{
                cur->next = pHead2;
                pHead2 = pHead2->next;
            }
            cur = cur->next;
        }
        cur->next = pHead1 ? pHead1 : pHead2;
        return dummy->next;
    }
};

class Solution:
    def Merge(self , pHead1: ListNode, pHead2: ListNode) -> ListNode:
        # write code here
        dummy = cur = ListNode(0)
        while pHead1 and pHead2:
            if pHead1.val <= pHead2.val:
                cur.next = pHead1
                pHead1 = pHead1.next
            else:
                cur.next = pHead2
                pHead2 = pHead2.next
            cur = cur.next
        cur.next = pHead1 if pHead1 else pHead2 
        return dummy.next

class Solution {
public:
    ListNode* Merge(ListNode* pHead1, ListNode* pHead2) {
        if(pHead1==nullptr || pHead2 == nullptr){
            return pHead1 ? pHead1 : pHead2;
        }
        if(pHead1->val <= pHead2->val){
            pHead1->next = Merge(pHead1->next, pHead2);
            return pHead1;
        }
        else{
            pHead2->next = Merge(pHead1, pHead2->next);
            return pHead2;
        }
    }
};

class Solution:
    def Merge(self , pHead1: ListNode, pHead2: ListNode) -> ListNode:
        # write code here
        if (pHead1==None): return pHead2
        if (pHead2==None): return pHead1
        
        if pHead1.val <= pHead2.val:
            pHead1.next = self.Merge(pHead1.next, pHead2)
            return pHead1
        else:
            pHead2.next = self.Merge(pHead1, pHead2.next)
            return pHead2