pub fn last_positions(tour_nodes: &[usize]) -> Vec<usize> {
let n = tour_nodes.iter().max().unwrap() + 1;
let mut pos = vec![None; n];
tour_nodes
.iter()
.enumerate()
.for_each(|(i, &u)| pos[u] = Some(i));
pos.iter().map(|&p| p.unwrap()).collect()
}
pub fn first_positions(tour_nodes: &[usize]) -> Vec<usize> {
let size = tour_nodes.len();
let mut tour = tour_nodes.to_vec();
tour.reverse();
last_positions(&tour).iter().map(|&i| size - i - 1).collect()
}