Merge Two Sorted Lists

01 · Question

You are given the heads of two sorted linked lists list1 and list2. Merge the two lists into one sorted list and return its head.

02 · Solution

Reference solution

1def mergeTwoLists(list1: Optional[ListNode], list2: Optional[ListNode]) -> Optional[ListNode]:
2    dummy = ListNode(0)
3    tail = dummy
4    
5    while list1 and list2:
6        if list1.val <= list2.val:
7            tail.next = list1
8            list1 = list1.next
9        else:
10            tail.next = list2
11            list2 = list2.next
12        tail = tail.next
13    
14    tail.next = list1 if list1 else list2
15    return dummy.next

Reverse Linked List

Linked List Cycle