Problem

Given the head of a singly linked list, compute an answer for every node.

For the node at position i, look to the nodes that appear after it in the list and return the value of the first node whose value is strictly greater than the current node value. If no such node exists, the answer for that position is 0.

Return the answers in the same order as the nodes appear in the list.

Notes

• The list is singly linked, so you can only move forward through it.
• The "next greater" node for a position is the first later node with a larger value, not necessarily the maximum value to the right.

Input Format

• A singly linked list represented by its head node.

Output Format

• An array of integers where the i-th value is the next greater value for the i-th list node, or 0 if none exists.

Constraints

• The list length is at least 1.
• Node values are integers.
• The list size is small enough to require an efficient solution better than checking every pair in the worst case.

Hints

• Think about how to remember nodes whose next greater value has not been found yet.
• A stack that keeps values in decreasing order can help resolve multiple nodes at once.
• If the linked list makes random access awkward, you may first collect values into a linear structure and then process them.