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Merge Two Sorted Lists

You are given the heads of two sorted linked lists list1 and list2. Merge the two lists into one sorted list. The list should be made by splicing together the nodes of the first two lists. Return the head of the merged linked list.

Runtime 0ms Memory 19.32 MB
def mergeTwoLists(list1: Optional[ListNode], list2: Optional[ListNode]) -> Optional[ListNode]:
    res = ListNode()
    temp = res
    while list1 or list2:
        curr1 = list1.val if list1 else float('inf')
        curr2 = list2.val if list2 else float('inf')
        if curr1 < curr2:
            temp.next = list1
            list1 = list1.next
        else:
            temp.next = list2
            list2 = list2.next
        temp = temp.next
    return res.next