1669-merge-in-between-linked-lists.py

class Solution:
    def mergeInBetween(self, list1: ListNode, a: int, b: int, list2: ListNode) -> ListNode:
        curr = list1
        i = 0
        while i < a - 1:
            curr = curr.next
            i += 1

        head = curr
        while i <= b:
            curr = curr.next
            i += 1
        head.next = list2

        while list2.next:
            list2 = list2.next
        list2.next = curr
        return list1