Merge Two Sorted Lists

LeetCode

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.

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
Previous
Reverse Linked List
Next
Linked List Cycle
i
1
0
2
1
4
2
|
3
j
1
4
3
5
4
6
merged=[]
Step 1 / 7
Step 1:
Initialize dummy and tail. Compare list1[0] and list2[0].
Pointers: i=0, j=4
Focus: compare @ [0, 4]