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| 1 | +use std::collections::{HashMap, HashSet, VecDeque}; |
| 2 | + |
| 3 | +// 815. Bus Routes, Hard |
| 4 | +// https://leetcode.com/problems/bus-routes/ |
| 5 | +impl Solution { |
| 6 | + pub fn num_buses_to_destination(routes: Vec<Vec<i32>>, source: i32, target: i32) -> i32 { |
| 7 | + let mut hm: HashMap<i32, Vec<(i32, i32)>> = HashMap::new(); |
| 8 | + |
| 9 | + for (bus, route) in routes.iter().enumerate() { |
| 10 | + let bus = bus as i32; |
| 11 | + |
| 12 | + let mut route = route.clone(); |
| 13 | + route.push(route[0]); |
| 14 | + |
| 15 | + for j in 0..route.len() - 1 { |
| 16 | + let j = j as i32; |
| 17 | + hm.entry(route[j as usize]) |
| 18 | + .and_modify(|f| f.push((route[j as usize + 1], bus))) |
| 19 | + .or_insert(vec![(route[j as usize + 1], bus)]); |
| 20 | + } |
| 21 | + } |
| 22 | + |
| 23 | + let mut queue: VecDeque<(i32, HashSet<i32>)> = VecDeque::new(); |
| 24 | + queue.push_back((source, HashSet::<i32>::new())); |
| 25 | + |
| 26 | + let mut seen: HashSet<i32> = HashSet::new(); |
| 27 | + |
| 28 | + let mut min_busses = usize::MAX; |
| 29 | + |
| 30 | + while !queue.is_empty() { |
| 31 | + let (stop, busses) = queue.pop_front().unwrap(); |
| 32 | + |
| 33 | + if stop == target { |
| 34 | + min_busses = min_busses.min(busses.len()); |
| 35 | + } |
| 36 | + |
| 37 | + seen.insert(stop); |
| 38 | + |
| 39 | + for edge in hm.get(&stop).unwrap_or(&vec![]) { |
| 40 | + if seen.contains(&edge.0) { |
| 41 | + continue; |
| 42 | + } |
| 43 | + |
| 44 | + let mut busses = busses.clone(); |
| 45 | + busses.insert(edge.1); |
| 46 | + queue.push_back((edge.0, busses)); |
| 47 | + } |
| 48 | + } |
| 49 | + |
| 50 | + min_busses as i32 |
| 51 | + } |
| 52 | +} |
| 53 | + |
| 54 | +struct Solution {} |
| 55 | + |
| 56 | +#[cfg(test)] |
| 57 | +mod tests { |
| 58 | + use super::*; |
| 59 | + use crate::vec_vec_i32; |
| 60 | + |
| 61 | + #[test] |
| 62 | + fn test_num_buses_to_destination() { |
| 63 | + assert_eq!(Solution::num_buses_to_destination(vec_vec_i32![[1, 2, 7], [3, 6, 7]], 1, 6), 2); |
| 64 | + } |
| 65 | + |
| 66 | + #[test] |
| 67 | + fn test_num_buses_to_destination2() { |
| 68 | + assert_eq!( |
| 69 | + Solution::num_buses_to_destination(vec_vec_i32![[7, 12], [4, 5, 15], [6], [15, 19], [9, 12, 13]], 15, 12), |
| 70 | + -1 |
| 71 | + ); |
| 72 | + } |
| 73 | +} |
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