Improved task 225

src/main/kotlin/g0201_0300/s0225_implement_stack_using_queues/MyStack.kt

@@ -1,66 +1,43 @@
 package g0201_0300.s0225_implement_stack_using_queues
 
-// #Easy #Stack #Design #Queue #2022_10_26_Time_248_ms_(73.44%)_Space_36.1_MB_(43.75%)
+// #Easy #Stack #Design #Queue #2024_08_17_Time_147_ms_(88.57%)_Space_35.9_MB_(87.62%)
 
 import java.util.LinkedList
+import java.util.Queue
 
-class MyStack {
-    private var queuePair = Pair(LinkedList<Int>(), LinkedList<Int>())
-    private var top: Int? = null
+class MyStack() {
+    private val queue1: Queue<Int> = LinkedList()
+    private val queue2: Queue<Int> = LinkedList()
 
     fun push(x: Int) {
-        queuePair.first.addLast(x)
-        top = x
+        queue1.add(x)
     }
 
     fun pop(): Int {
-        if (isQueuesEmpty()) {
-            throw Exception()
+        while (queue1.size > 1) {
+            queue2.add(queue1.remove())
         }
-        val queuePair = selectSourceAndDestinationQueues(queuePair)
-        var value = 0
-        repeat(queuePair.first.size) {
-            when (queuePair.first.size) {
-                2 -> {
-                    top = queuePair.first.removeFirst()
-                    queuePair.second.addLast(top)
-                }
-                1 -> {
-                    value = queuePair.first.removeFirst()
-                }
-                else -> {
-                    queuePair.second.addLast(queuePair.first.removeFirst())
-                }
-            }
-        }
-        return value
+        val top = queue1.remove()
+        queue1.clear()
+        queue1.addAll(queue2)
+        queue2.clear()
+        return top
     }
 
     fun top(): Int {
-        if (isQueuesEmpty()) {
-            throw Exception()
+        while (queue1.size > 1) {
+            queue2.add(queue1.remove())
         }
-        return top!!
+        val top = queue1.remove()
+        queue2.add(top)
+        queue1.clear()
+        queue1.addAll(queue2)
+        queue2.clear()
+        return top
     }
 
     fun empty(): Boolean {
-        return isQueuesEmpty()
-    }
-
-    private fun isQueuesEmpty(): Boolean {
-        if (queuePair.first.isEmpty() && queuePair.second.isEmpty()) {
-            return true
-        }
-        return false
-    }
-
-    private fun selectSourceAndDestinationQueues(queuePair: Pair<LinkedList<Int>, LinkedList<Int>>):
-        Pair<LinkedList<Int>, LinkedList<Int>> {
-        return if (queuePair.first.isNotEmpty()) {
-            Pair(queuePair.first, queuePair.second)
-        } else {
-            Pair(queuePair.second, queuePair.first)
-        }
+        return queue1.isEmpty()
     }
 }