Create 815-bus-routes.js

Author: everthis

815-bus-routes.js

@@ -0,0 +1,38 @@
+/**
+ * @param {number[][]} routes
+ * @param {number} S
+ * @param {number} T
+ * @return {number}
+ */
+const numBusesToDestination = function (routes, S, T) {
+  if (S === T) return 0
+  const map = {}
+  const visited = new Array(routes.length).fill(false),
+    queue = [S]
+  let rides = 0
+  for (let i = 0; i < routes.length; i++) {
+    for (const stop of routes[i]) {
+      if (map[stop] === undefined) {
+        map[stop] = []
+      }
+      map[stop].push(i)
+    }
+  }
+  while (queue.length > 0) {
+    let size = queue.length
+    rides += 1
+    while (size > 0) {
+      const currStop = queue.shift()
+      size -= 1
+      for (const bus of map[currStop]) {
+        if (visited[bus]) continue
+        visited[bus] = true
+        for (const stop of routes[bus]) {
+          if (stop === T) return rides
+          queue.push(stop)
+        }
+      }
+    }
+  }
+  return -1
+}