Two Sum and Linked List Reversal

DoorDash routing utilities need two independent algorithms: identify two delivery indices whose priorities reach a target, then reverse a linked list of delivery stops. Implement both operations in one function.

Given an integer array nums, an integer target, and the head of a singly linked list, return the indices of two values that sum to target and the new head after reversing the linked list.

For JSON compatibility, each linked-list node is represented as a dictionary with keys val and next. The next value is another node dictionary or null.

Formal Specification

Implement two_sum_and_reverse(nums, target, head).

• nums is a list of integers.
• target is an integer.
• head is a linked-list node dictionary or null.
• Return a dictionary with two_sum, a two-element list of indices in ascending order, and reversed_head, the new linked-list head.
• Each input has exactly one valid Two Sum pair.
• Reverse the list by changing node pointers, not by copying values into a new list.