Merge pull request #2582 from aadil42/patch-54

Author: aakhtar3

javascript/1396-design-underground-system.js

@@ -0,0 +1,54 @@
+// https://leetcode.com/problems/design-underground-system/
+class UndergroundSystem {
+  constructor() {
+    this.stationSystem = {};
+    this.averageTime = {};
+  }
+
+  /**
+   * Time O(1) | Space O(1)
+   * Records the check-in time and station for a user.
+   * @param {number} id - User ID
+   * @param {string} stationName - Check-in station name
+   * @param {number} t - Check-in time
+   * @return {void}
+   */
+  checkIn(id, stationName, t) {
+    this.stationSystem[id] = [stationName, '', t, ''];
+  }
+
+  /**
+   * Time O(1) | Space O(1)
+   * Records the check-out time and station for a user, and calculates the average time.
+   * @param {number} id - User ID
+   * @param {string} stationName - Check-out station name
+   * @param {number} t - Check-out time
+   * @return {void}
+   */
+  checkOut(id, stationName, t) {
+    const user = this.stationSystem[id];
+    user[1] = stationName;
+    user[3] = t;
+    const stationHash = `${user[0]}-${user[1]}`;
+    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)
+   * Returns the average time taken to travel between two stations.
+   * @param {string} startStation - Start station name
+   * @param {string} endStation - End station name
+   * @return {number} - Average time in hours
+   */
+  getAverageTime(startStation, endStation) {
+    const [rounds, totalHours] = this.averageTime[`${startStation}-${endStation}`];
+    return totalHours / rounds;
+  }
+}