Update index.ts

Author: masx200

design-underground-system/index.ts

@@ -1,13 +1,35 @@
 export default class UndergroundSystem {
+    id2info = new Map<number, [string, number]>();
+    station2time = new Map<string, number[]>();
     constructor() {
     }
 
     checkIn(id: number, stationName: string, t: number): void {
+        const info: [string, number] = [stationName, t];
+        this.id2info.set(id, info);
     }
 
     checkOut(id: number, stationName: string, t: number): void {
+        const info = this.id2info.get(id);
+        if (info) {
+            const key = JSON.stringify([info[0], stationName]);
+            const time = this.station2time.get(
+                key,
+            ) ?? [];
+            time.push(t - info[1]);
+            this.station2time.set(key, time);
+        } else {
+            throw Error("accident");
+        }
     }
 
     getAverageTime(startStation: string, endStation: string): number {
+        const key = JSON.stringify([startStation, endStation]);
+        const time = this.station2time.get(
+            key,
+        );
+        if (!time) throw Error("accident");
+
+        return time.reduce((a, v) => a + v, 0) / time.length;
     }
 }