Create 1396-design-underground-system.js

Adding solution for design-underground-system in JS.

Author: aadil42

javascript/1396-design-underground-system.js

@@ -0,0 +1,60 @@
+var UndergroundSystem = function() {
+    this.stationSystem = {};
+    this.averageTime = {};
+};
+
+/** 
+ * https://leetcode.com/problems/design-underground-system
+ * Time O(1) | Space O(1)
+ * @param {number} id 
+ * @param {string} stationName 
+ * @param {number} t
+ * @return {void}
+ */
+UndergroundSystem.prototype.checkIn = function(id, stationName, t) {
+    this.stationSystem[id] = [stationName, '', t, ''];
+};
+
+/** Time O(1) | Space O(1)
+ * @param {number} id 
+ * @param {string} stationName 
+ * @param {number} t
+ * @return {void}
+ */
+UndergroundSystem.prototype.checkOut = function(id, stationName, t) {
+    const user = this.stationSystem[id];
+    //1 is the position where we store end station
+    // 3 is the position where we store end time
+    user[1] = stationName;
+    user[3] = t; 
+    console.log(user);
+    const stationHash = `${user[0]}-${user[1]}`;
+    // console.log(stationHash, this.stationHash);
+    if(this.averageTime[stationHash]) {
+        this.averageTime[stationHash][0] += 1;
+        this.averageTime[stationHash][1] += user[3] - user[2];
+    } else {
+        this.averageTime[stationHash] = [];
+        this.averageTime[stationHash][0] = 1;
+        this.averageTime[stationHash][1] = user[3] - user[2];
+    }
+};
+
+/** Time O(1) | Space O(1)
+ * @param {string} startStation 
+ * @param {string} endStation
+ * @return {number}
+ */
+UndergroundSystem.prototype.getAverageTime = function(startStation, endStation) {
+    // console.log(this.averageTime);
+    const [rounds, totalHours] = this.averageTime[`${startStation}-${endStation}`];
+    return totalHours / rounds;
+};
+
+/** 
+ * 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)
+ */