pub fn num_buses_to_destination(routes: Vec<Vec<i32>>, source: i32, target: i32) -> i32 {

let mut hm: HashMap<i32, Vec<(i32, i32)>> = HashMap::new();

for (bus, route) in routes.iter().enumerate() {

let bus = bus as i32;

let mut route = route.clone();

route.push(route[0]);

for j in 0..route.len() - 1 {

let j = j as i32;

hm.entry(route[j as usize])

.and_modify(|f| f.push((route[j as usize + 1], bus)))

.or_insert(vec![(route[j as usize + 1], bus)]);

}

}

let mut queue: VecDeque<(i32, HashSet<i32>)> = VecDeque::new();

queue.push_back((source, HashSet::<i32>::new()));

let mut seen: HashSet<i32> = HashSet::new();

let mut min_busses = usize::MAX;

while !queue.is_empty() {

let (stop, busses) = queue.pop_front().unwrap();

if stop == target {

min_busses = min_busses.min(busses.len());

}

seen.insert(stop);

for edge in hm.get(&stop).unwrap_or(&vec![]) {

if seen.contains(&edge.0) {

continue;

}

let mut busses = busses.clone();

busses.insert(edge.1);

queue.push_back((edge.0, busses));

}

}

min_busses as i32

}

use super::*;

use crate::vec_vec_i32;

#[test]

fn test_num_buses_to_destination() {

assert_eq!(Solution::num_buses_to_destination(vec_vec_i32![[1, 2, 7], [3, 6, 7]], 1, 6), 2);

}

#[test]

fn test_num_buses_to_destination2() {

assert_eq!(

Solution::num_buses_to_destination(vec_vec_i32![[7, 12], [4, 5, 15], [6], [15, 19], [9, 12, 13]], 15, 12),

-1

);

}