Create 1396-design-underground-system.js

Author: everthis

1396-design-underground-system.js

@@ -0,0 +1,49 @@
+
+const UndergroundSystem = function() {
+  this.h = new Map()
+  this.routeMap = new Map()
+};
+
+/** 
+ * @param {number} id 
+ * @param {string} stationName 
+ * @param {number} t
+ * @return {void}
+ */
+UndergroundSystem.prototype.checkIn = function(id, stationName, t) {
+  this.h.set(id, [stationName, t])
+};
+
+/** 
+ * @param {number} id 
+ * @param {string} stationName 
+ * @param {number} t
+ * @return {void}
+ */
+UndergroundSystem.prototype.checkOut = function(id, stationName, t) {
+  const [sn, st] = this.h.get(id)
+  this.h.delete(id)
+  const route = `${sn},${stationName}`
+  const duration = t - st
+  const [totalTime, totalValue] = this.routeMap.get(route) || ([0, 0])
+  this.routeMap.set(route, [totalTime + duration, totalValue + 1])
+};
+
+/** 
+ * @param {string} startStation 
+ * @param {string} endStation
+ * @return {number}
+ */
+UndergroundSystem.prototype.getAverageTime = function(startStation, endStation) {
+  const k = `${startStation},${endStation}`
+  const [time, number] = this.routeMap.get(k)
+  return time / number
+};
+
+/** 
+ * Your UndergroundSystem object will be instantiated and called as such:
+ * var obj = new UndergroundSystem()
+ * obj.checkIn(id,stationName,t)
+ * obj.checkOut(id,stationName,t)
+ * var param_3 = obj.getAverageTime(startStation,endStation)
+ */