Create 1396.设计地铁系统.js

Author: yinxin630

1396.设计地铁系统.js

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+
+var UndergroundSystem = function() {
+    this.in = new Map();
+    this.check = new Map();
+};
+
+/** 
+ * @param {number} id 
+ * @param {string} stationName 
+ * @param {number} t
+ * @return {void}
+ */
+UndergroundSystem.prototype.checkIn = function(id, stationName, t) {
+    this.in.set(id, [stationName, t]);
+};
+
+/** 
+ * @param {number} id 
+ * @param {string} stationName 
+ * @param {number} t
+ * @return {void}
+ */
+UndergroundSystem.prototype.checkOut = function(id, stationName, t) {
+    const [a, b] = this.in.get(id);
+    const key = a + ':' + stationName;
+    const check = this.check.get(key);
+    if (check) {
+        this.check.set(key, [t - b + check[0], 1 + check[1]]);
+    } else {
+        this.check.set(key, [t - b, 1]);
+    }
+};
+
+/** 
+ * @param {string} startStation 
+ * @param {string} endStation
+ * @return {number}
+ */
+UndergroundSystem.prototype.getAverageTime = function(startStation, endStation) {
+    const key = startStation + ':' + endStation;
+    const check = this.check.get(key);
+    if (!check) {
+        return 0;
+    } else {
+        return check[0] / check[1];
+    }
+};
+
+/**
+ * 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)
+ */