1669. Merge In Between Linked Lists

class Solution {
   public ListNode mergeInBetween(ListNode list1, int a, int b, ListNode list2) {
        ListNode curr = list1;
        int i = 0;

        while (i < a - 1) {
            curr = curr.next;
            i++;
        }

        ListNode beforeA = curr;
        while (i < b) {
            curr = curr.next;
            i++;
        }

        ListNode afterB = curr.next;

        beforeA.next = list2;

        ListNode endOfList2 = list2;
        while (endOfList2.next != null) {
            endOfList2 = endOfList2.next;
        }

        endOfList2.next = afterB;
        return list1;

    }
}