Create 1396-design-underground-system.kt

Author: a93a

Diff for: kotlin/1396-design-underground-system.kt

@@ -0,0 +1,22 @@
+class UndergroundSystem() {
+
+    val checkIn = HashMap<Int, Pair<String, Int>>() // id -> (startStation to time)
+    val averageTime = HashMap<String, Pair<Double, Int>>() // startion -> (TotalTime to countOfTrips)
+
+    fun checkIn(id: Int, start: String, startTime: Int) {
+        checkIn[id] = start to startTime
+    }
+
+    fun checkOut(id: Int, end: String, endTime: Int) {
+        val (start, startTime) = checkIn[id]!!
+        val fromTo = "$start:$end"
+        val (total, count) = averageTime.getOrDefault(fromTo, 0.0 to 0)
+        averageTime[fromTo] = (total + endTime - startTime) to (count + 1)
+    }
+
+    fun getAverageTime(start: String, end: String): Double {
+        val (total, count) = averageTime.getOrDefault("$start:$end", 0.0 to 0)
+        return total / count
+    }
+
+}