Compress vertices into uniques and indices

You are given an array of vertices (a 2D array). Each vertex may repeat. Implement a simple “compression” that produces: 1. `unique_vertices`: the list of unique vertices, **preserving the order of first appearance**. 2. `indices`: for each vertex in the original array, the index of its corresponding vertex in `unique_vertices`. ### Input - `vertices`: a list of `n` vertices - each vertex is a fixed-length list/tuple of integers (e.g., 3D vertex) ### Output - `unique_vertices`: list of unique vertices in first-seen order - `indices`: integer list of length `n` ### Example Input: ``` [[2,2,2], [0,1,0], [2,1,2], [0,1,0]] ``` Output: ``` unique_vertices = [[2,2,2], [0,1,0], [2,1,2]] indices = [0, 1, 2, 1] ``` ### Notes / Constraints - Treat two vertices as equal if all coordinates match. - Aim for efficient time complexity (better than O(n^2) if possible).