Question
You are given a list of positive integers. Return the last value in the list that appears exactly once in the entire list — that is, among all values with a total count of 1, the one whose position is furthest to the right. If every value occurs two or more times, or the list is empty, return -1. For example, in [4, 7, 4, 9, 7, 2] both 9 and 2 appear once, and 2 sits further right, so the answer is 2.
last_unique_value(nums: list[int]) → int[[4,7,4,9,7,2]]out2State your approach and its time/space complexity out loud before you optimize. Handle the edge cases (empty input, duplicates, overflow), and say why you chose this over the brute force. Green tests are the floor, not the grade.
Vibe coding: describe the solution in plain language (or narrate it) and the coach grades your approach. Generating runnable code from your description is coming next.