20240917 finished.

src/problem/mod.rs

@@ -238,3 +238,4 @@ mod p2398_maximum_number_of_robots_within_budget;
 mod p2390_removing_stars_from_a_string;
 mod p2848_points_that_intersect_with_cars;
 mod p1184_distance_between_bus_stops;
+mod p815_bus_routes;

src/problem/p815_bus_routes.rs

@@ -0,0 +1,90 @@
+/**
+ * [815] Bus Routes
+ */
+pub struct Solution {}
+
+
+// submission codes start here
+
+impl Solution {
+    pub fn num_buses_to_destination(routes: Vec<Vec<i32>>, source: i32, target: i32) -> i32 {
+        use std::collections::{VecDeque, HashMap};
+        
+        if source == target {
+            return 0;
+        }
+
+        let n = routes.len();
+        // 存储经过某一站的公交线路
+        let mut map: HashMap<i32, Vec<usize>> = HashMap::new();
+        // 存储不同公交线路之前的联通情况
+        let mut edge = vec![vec![false; n]; n];
+
+        for (bus, stations) in routes.iter().enumerate() {
+            for &station in stations {
+                if let Some(connected_stations) = map.get(&station) {
+                    for &connected_station in connected_stations {
+                        edge[connected_station][bus] = true;
+                        edge[bus][connected_station] = true;
+                    }
+                }
+
+                let entry = map.entry(station).or_insert(vec![]);
+                entry.push(bus);
+            }
+        }
+
+        let mut distances = vec![-1; n];
+        let mut queue = VecDeque::new();
+        
+        if let Some(source_buses) = map.get(&source) {
+            for &bus in source_buses {
+                distances[bus] = 1;
+                queue.push_back(bus);    
+            }
+        } else { 
+            // 没有任何公交车经过起始站点
+            return -1;
+        }
+
+        while !queue.is_empty() {
+            let now = queue.pop_front().unwrap();
+
+            for next in 0..n {
+                if edge[now][next] && distances[next] == -1 {
+                    distances[next] = distances[now] + 1;
+                    queue.push_back(next);
+                }
+            }
+        }
+
+        let mut result = i32::MAX;
+
+        if let Some(target_buses) = map.get(&target) {
+            for &bus in target_buses {
+                result = result.min(distances[bus]);
+            }
+        } else { 
+            // 没有任何公交车经过终点站点
+            return -1;
+        }
+
+        if result == i32::MAX {
+            -1
+        } else { 
+            result
+        }
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_815() {
+        assert_eq!(2, Solution::num_buses_to_destination(vec![vec![1, 2, 7], vec![3, 6, 7]], 1, 6));
+    }
+}