From 4badbec94341d381d332f1fe8a794628302ac4b7 Mon Sep 17 00:00:00 2001
From: Claudio Maggioni <claudio@maggioni.xyz>
Date: Thu, 17 Oct 2019 10:36:41 +0200
Subject: [PATCH] hw1: Make the Queues actually Queues and not stacks

---
 hw1/Ex2/.idea/workspace.xml                  | 215 +++++++++----------
 hw1/Ex2/src/explicit/ExplicitValetQueue.java |  20 +-
 hw1/Ex2/src/implicit/ImplicitValetQueue.java |  20 +-
 hw1/Ex2/src/semaphore/ValetQueue.java        |  13 +-
 4 files changed, 145 insertions(+), 123 deletions(-)

diff --git a/hw1/Ex2/.idea/workspace.xml b/hw1/Ex2/.idea/workspace.xml
index 8a90dee..b98dee7 100644
--- a/hw1/Ex2/.idea/workspace.xml
+++ b/hw1/Ex2/.idea/workspace.xml
@@ -2,26 +2,10 @@
 <project version="4">
   <component name="ChangeListManager">
     <list default="true" id="b097df70-ddbc-49a8-ab62-9674f3f49e84" name="Default Changelist" comment="">
-      <change afterPath="$PROJECT_DIR$/../../IE1/.idea/compiler.xml" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/../../IE1/.idea/libraries/Maven__junit_junit_4_12.xml" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/../../IE1/.idea/libraries/Maven__org_hamcrest_hamcrest_core_1_3.xml" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/../../IE1/.idea/misc.xml" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/../../IE1/.idea/modules.xml" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/../../IE1/.idea/vcs.xml" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/../../IE1/IE1.iml" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/../../IE1/pom.xml" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/../../IE1/src/semaphore/MyBulkSemaphore.java" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/../../IE1/src/semaphore/MySemaphore.java" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/.idea/Ex2.iml" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/src/explicit/ExplicitValetQueue.java" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/src/explicit/Main.java" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/src/implicit/ImplicitValetQueue.java" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/src/implicit/Main.java" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/../Ex1/.idea/workspace.xml" beforeDir="false" afterPath="$PROJECT_DIR$/../Ex1/.idea/workspace.xml" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/src/semaphore/Car.java" beforeDir="false" afterPath="$PROJECT_DIR$/src/semaphore/Car.java" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/src/semaphore/Main.java" beforeDir="false" afterPath="$PROJECT_DIR$/src/semaphore/Main.java" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/.idea/workspace.xml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/workspace.xml" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/src/explicit/ExplicitValetQueue.java" beforeDir="false" afterPath="$PROJECT_DIR$/src/explicit/ExplicitValetQueue.java" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/src/implicit/ImplicitValetQueue.java" beforeDir="false" afterPath="$PROJECT_DIR$/src/implicit/ImplicitValetQueue.java" afterDir="false" />
       <change beforePath="$PROJECT_DIR$/src/semaphore/ValetQueue.java" beforeDir="false" afterPath="$PROJECT_DIR$/src/semaphore/ValetQueue.java" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/../submission.tex" beforeDir="false" afterPath="$PROJECT_DIR$/../submission.tex" afterDir="false" />
     </list>
     <option name="EXCLUDED_CONVERTED_TO_IGNORED" value="true" />
     <option name="SHOW_DIALOG" value="false" />
@@ -30,19 +14,18 @@
     <option name="LAST_RESOLUTION" value="IGNORE" />
   </component>
   <component name="DefaultGradleProjectSettings">
-    <option name="testRunner" value="GRADLE" />
-    <option name="delegatedBuild" value="true" />
+    <option name="isMigrated" value="true" />
   </component>
   <component name="FileEditorManager">
-    <leaf>
+    <leaf SIDE_TABS_SIZE_LIMIT_KEY="300">
       <file pinned="false" current-in-tab="false">
         <entry file="file://$PROJECT_DIR$/src/semaphore/Car.java">
           <provider selected="true" editor-type-id="text-editor">
             <state relative-caret-position="315">
-              <caret line="25" column="13" lean-forward="true" selection-start-line="25" selection-start-column="13" selection-end-line="25" selection-end-column="13" />
+              <caret line="25" column="13" selection-start-line="25" selection-start-column="13" selection-end-line="25" selection-end-column="13" />
               <folding>
                 <element signature="e#502#503#0" expanded="true" />
-                <element signature="e#532#533#0" expanded="true" />
+                <element signature="e#526#527#0" expanded="true" />
               </folding>
             </state>
           </provider>
@@ -51,8 +34,8 @@
       <file pinned="false" current-in-tab="false">
         <entry file="file://$PROJECT_DIR$/src/semaphore/ValetQueue.java">
           <provider selected="true" editor-type-id="text-editor">
-            <state relative-caret-position="195">
-              <caret line="15" column="32" lean-forward="true" selection-start-line="15" selection-start-column="32" selection-end-line="15" selection-end-column="32" />
+            <state relative-caret-position="135">
+              <caret line="11" lean-forward="true" selection-start-line="11" selection-end-line="11" />
             </state>
           </provider>
         </entry>
@@ -60,8 +43,8 @@
       <file pinned="false" current-in-tab="false">
         <entry file="file://$PROJECT_DIR$/src/implicit/ImplicitValetQueue.java">
           <provider selected="true" editor-type-id="text-editor">
-            <state relative-caret-position="60">
-              <caret line="9" column="13" selection-start-line="9" selection-start-column="13" selection-end-line="9" selection-end-column="13" />
+            <state relative-caret-position="240">
+              <caret line="21" column="9" selection-start-line="21" selection-start-column="9" selection-end-line="21" selection-end-column="9" />
             </state>
           </provider>
         </entry>
@@ -75,11 +58,11 @@
           </provider>
         </entry>
       </file>
-      <file pinned="false" current-in-tab="false">
+      <file pinned="false" current-in-tab="true">
         <entry file="file://$PROJECT_DIR$/src/semaphore/Main.java">
           <provider selected="true" editor-type-id="text-editor">
-            <state relative-caret-position="195">
-              <caret line="13" column="65" selection-start-line="13" selection-start-column="65" selection-end-line="13" selection-end-column="65" />
+            <state relative-caret-position="135">
+              <caret line="9" column="43" selection-start-line="9" selection-start-column="43" selection-end-line="9" selection-end-column="43" />
             </state>
           </provider>
         </entry>
@@ -87,8 +70,8 @@
       <file pinned="false" current-in-tab="false">
         <entry file="file://$PROJECT_DIR$/src/explicit/Main.java">
           <provider selected="true" editor-type-id="text-editor">
-            <state relative-caret-position="225">
-              <caret line="15" lean-forward="true" selection-start-line="15" selection-end-line="15" />
+            <state relative-caret-position="180">
+              <caret line="15" selection-start-line="15" selection-end-line="15" />
               <folding>
                 <element signature="imports" expanded="true" />
               </folding>
@@ -105,11 +88,11 @@
           </provider>
         </entry>
       </file>
-      <file pinned="false" current-in-tab="true">
+      <file pinned="false" current-in-tab="false">
         <entry file="file://$PROJECT_DIR$/src/explicit/ExplicitValetQueue.java">
           <provider selected="true" editor-type-id="text-editor">
-            <state relative-caret-position="70">
-              <caret line="36" column="62" selection-start-line="36" selection-start-column="62" selection-end-line="36" selection-end-column="62" />
+            <state relative-caret-position="168">
+              <caret line="22" selection-start-line="22" selection-end-line="26" />
             </state>
           </provider>
         </entry>
@@ -133,27 +116,17 @@
       <list>
         <option value="$PROJECT_DIR$/src/semaphore/Car.java" />
         <option value="$PROJECT_DIR$/src/semaphore/ImplicitValetQueue.java" />
-        <option value="$PROJECT_DIR$/src/semaphore/ValetQueue.java" />
         <option value="$PROJECT_DIR$/src/semaphore/ExplicitValetQueue.java" />
-        <option value="$PROJECT_DIR$/src/semaphore/Main.java" />
         <option value="$PROJECT_DIR$/src/explicit/Main.java" />
         <option value="$PROJECT_DIR$/src/implicit/Main.java" />
         <option value="$PROJECT_DIR$/src/explicit/ExplicitValetQueue.java" />
+        <option value="$PROJECT_DIR$/src/implicit/ImplicitValetQueue.java" />
+        <option value="$PROJECT_DIR$/src/semaphore/ValetQueue.java" />
+        <option value="$PROJECT_DIR$/src/semaphore/Main.java" />
       </list>
     </option>
   </component>
-  <component name="ProjectConfigurationFiles">
-    <option name="files">
-      <list>
-        <option value="$PROJECT_DIR$/.idea/Ex2.iml" />
-        <option value="$PROJECT_DIR$/.idea/misc.xml" />
-        <option value="$PROJECT_DIR$/.idea/vcs.xml" />
-        <option value="$PROJECT_DIR$/.idea/modules.xml" />
-        <option value="$PROJECT_DIR$/.idea/uiDesigner.xml" />
-      </list>
-    </option>
-  </component>
-  <component name="ProjectFrameBounds" extendedState="6">
+  <component name="ProjectFrameBounds" fullScreen="true">
     <option name="width" value="1680" />
     <option name="height" value="1050" />
   </component>
@@ -163,8 +136,6 @@
       <foldersAlwaysOnTop value="true" />
     </navigator>
     <panes>
-      <pane id="Scope" />
-      <pane id="PackagesPane" />
       <pane id="ProjectPane">
         <subPane>
           <expand>
@@ -199,9 +170,12 @@
           <select />
         </subPane>
       </pane>
+      <pane id="PackagesPane" />
+      <pane id="Scope" />
     </panes>
   </component>
   <component name="PropertiesComponent">
+    <property name="SHARE_PROJECT_CONFIGURATION_FILES" value="true" />
     <property name="WebServerToolWindowFactoryState" value="false" />
     <property name="aspect.path.notification.shown" value="true" />
     <property name="last_opened_file_path" value="$PROJECT_DIR$" />
@@ -230,7 +204,7 @@
       </list>
     </option>
   </component>
-  <component name="RunManager" selected="Application.Main (1)">
+  <component name="RunManager" selected="Application.Main">
     <configuration name="Main (1)" type="Application" factoryName="Application" temporary="true" nameIsGenerated="true">
       <option name="MAIN_CLASS_NAME" value="explicit.Main" />
       <module name="Ex2" />
@@ -244,6 +218,19 @@
         <option name="Make" enabled="true" />
       </method>
     </configuration>
+    <configuration name="Main (2)" type="Application" factoryName="Application" temporary="true" nameIsGenerated="true">
+      <option name="MAIN_CLASS_NAME" value="implicit.Main" />
+      <module name="Ex2" />
+      <extension name="coverage">
+        <pattern>
+          <option name="PATTERN" value="implicit.*" />
+          <option name="ENABLED" value="true" />
+        </pattern>
+      </extension>
+      <method v="2">
+        <option name="Make" enabled="true" />
+      </method>
+    </configuration>
     <configuration name="Main" type="Application" factoryName="Application" temporary="true" nameIsGenerated="true">
       <option name="MAIN_CLASS_NAME" value="semaphore.Main" />
       <module name="Ex2" />
@@ -259,8 +246,9 @@
     </configuration>
     <recent_temporary>
       <list>
-        <item itemvalue="Application.Main (1)" />
         <item itemvalue="Application.Main" />
+        <item itemvalue="Application.Main (2)" />
+        <item itemvalue="Application.Main (1)" />
       </list>
     </recent_temporary>
   </component>
@@ -274,57 +262,69 @@
       <option name="number" value="Default" />
       <option name="presentableId" value="Default" />
       <updated>1571167105834</updated>
-      <workItem from="1571167107083" duration="2054000" />
+      <workItem from="1571167107083" duration="2304000" />
+      <workItem from="1571299023277" duration="932000" />
     </task>
     <servers />
   </component>
   <component name="TimeTrackingManager">
-    <option name="totallyTimeSpent" value="2054000" />
+    <option name="totallyTimeSpent" value="3236000" />
   </component>
   <component name="ToolWindowManager">
-    <frame x="0" y="23" width="1680" height="1027" extended-state="6" />
+    <frame x="0" y="0" width="1680" height="1050" extended-state="6" />
     <editor active="true" />
     <layout>
-      <window_info id="Designer" />
-      <window_info id="Image Layers" />
-      <window_info id="Capture Tool" />
-      <window_info id="UI Designer" />
-      <window_info id="Favorites" side_tool="true" />
-      <window_info id="Learn" />
-      <window_info content_ui="combo" id="Project" order="0" visible="true" weight="0.24969475" />
+      <window_info content_ui="combo" id="Project" order="0" visible="true" weight="0.25274727" />
       <window_info id="Structure" order="1" side_tool="true" weight="0.25" />
-      <window_info anchor="bottom" id="Terminal" />
-      <window_info anchor="bottom" id="Docker" show_stripe_button="false" />
-      <window_info anchor="bottom" id="Event Log" side_tool="true" />
-      <window_info anchor="bottom" id="Database Changes" />
-      <window_info anchor="bottom" id="Version Control" />
-      <window_info anchor="bottom" id="Messages" />
+      <window_info id="Designer" order="2" />
+      <window_info id="Image Layers" order="3" />
+      <window_info id="Capture Tool" order="4" />
+      <window_info id="UI Designer" order="5" />
+      <window_info id="Favorites" order="6" side_tool="true" />
+      <window_info id="Learn" order="7" />
       <window_info anchor="bottom" id="Message" order="0" />
       <window_info anchor="bottom" id="Find" order="1" />
-      <window_info active="true" anchor="bottom" id="Run" order="2" visible="true" weight="0.32941177" />
+      <window_info anchor="bottom" id="Run" order="2" weight="0.32857144" />
       <window_info anchor="bottom" id="Debug" order="3" weight="0.4" />
       <window_info anchor="bottom" id="Cvs" order="4" weight="0.25" />
       <window_info anchor="bottom" id="Inspection" order="5" weight="0.4" />
       <window_info anchor="bottom" id="TODO" order="6" />
-      <window_info anchor="right" id="Maven" />
-      <window_info anchor="right" id="Palette" />
-      <window_info anchor="right" id="Capture Analysis" />
-      <window_info anchor="right" id="Database" />
-      <window_info anchor="right" id="Palette&#9;" />
-      <window_info anchor="right" id="Theme Preview" />
+      <window_info anchor="bottom" id="Terminal" order="7" />
+      <window_info anchor="bottom" id="Docker" order="8" show_stripe_button="false" />
+      <window_info anchor="bottom" id="Event Log" order="9" side_tool="true" />
+      <window_info anchor="bottom" id="Messages" order="10" />
+      <window_info anchor="bottom" id="Database Changes" order="11" />
+      <window_info anchor="bottom" id="Version Control" order="12" />
       <window_info anchor="right" id="Commander" internal_type="SLIDING" order="0" type="SLIDING" weight="0.4" />
       <window_info anchor="right" id="Ant Build" order="1" weight="0.25" />
       <window_info anchor="right" content_ui="combo" id="Hierarchy" order="2" weight="0.25" />
+      <window_info anchor="right" id="Maven" order="3" />
+      <window_info anchor="right" id="Palette" order="4" />
+      <window_info anchor="right" id="Capture Analysis" order="5" />
+      <window_info anchor="right" id="Database" order="6" />
+      <window_info anchor="right" id="Palette&#9;" order="7" />
+      <window_info anchor="right" id="Theme Preview" order="8" />
     </layout>
   </component>
   <component name="TypeScriptGeneratedFilesManager">
     <option name="version" value="1" />
   </component>
   <component name="editorHistoryManager">
-    <entry file="file://$PROJECT_DIR$/src/semaphore/CarSimulation.java">
+    <entry file="jar:///Library/Java/JavaVirtualMachines/openjdk-12.0.1.jdk/Contents/Home/lib/src.zip!/java.base/java/util/concurrent/locks/ReentrantLock.java">
       <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="30">
-          <caret line="2" column="13" selection-start-line="2" selection-start-column="13" selection-end-line="2" selection-end-column="13" />
+        <state relative-caret-position="200">
+          <caret line="148" column="22" selection-start-line="148" selection-start-column="22" selection-end-line="148" selection-end-column="22" />
+        </state>
+      </provider>
+    </entry>
+    <entry file="file://$PROJECT_DIR$/src/semaphore/Car.java">
+      <provider selected="true" editor-type-id="text-editor">
+        <state relative-caret-position="315">
+          <caret line="25" column="13" selection-start-line="25" selection-start-column="13" selection-end-line="25" selection-end-column="13" />
+          <folding>
+            <element signature="e#502#503#0" expanded="true" />
+            <element signature="e#526#527#0" expanded="true" />
+          </folding>
         </state>
       </provider>
     </entry>
@@ -335,35 +335,41 @@
         </state>
       </provider>
     </entry>
-    <entry file="file://$PROJECT_DIR$/src/semaphore/Car.java">
+    <entry file="file://$PROJECT_DIR$/src/explicit/Main.java">
       <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="315">
-          <caret line="25" column="13" lean-forward="true" selection-start-line="25" selection-start-column="13" selection-end-line="25" selection-end-column="13" />
+        <state relative-caret-position="180">
+          <caret line="15" selection-start-line="15" selection-end-line="15" />
           <folding>
-            <element signature="e#502#503#0" expanded="true" />
-            <element signature="e#532#533#0" expanded="true" />
+            <element signature="imports" expanded="true" />
           </folding>
         </state>
       </provider>
     </entry>
-    <entry file="file://$PROJECT_DIR$/src/semaphore/Main.java">
+    <entry file="file://$PROJECT_DIR$/src/semaphore/CarSimulation.java">
       <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="195">
-          <caret line="13" column="65" selection-start-line="13" selection-start-column="65" selection-end-line="13" selection-end-column="65" />
+        <state relative-caret-position="30">
+          <caret line="2" column="13" selection-start-line="2" selection-start-column="13" selection-end-line="2" selection-end-column="13" />
         </state>
       </provider>
     </entry>
-    <entry file="file://$PROJECT_DIR$/src/semaphore/ValetQueue.java">
+    <entry file="file://$PROJECT_DIR$/src/explicit/ExplicitValetQueue.java">
       <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="195">
-          <caret line="15" column="32" lean-forward="true" selection-start-line="15" selection-start-column="32" selection-end-line="15" selection-end-column="32" />
+        <state relative-caret-position="168">
+          <caret line="22" selection-start-line="22" selection-end-line="26" />
         </state>
       </provider>
     </entry>
     <entry file="file://$PROJECT_DIR$/src/implicit/ImplicitValetQueue.java">
       <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="60">
-          <caret line="9" column="13" selection-start-line="9" selection-start-column="13" selection-end-line="9" selection-end-column="13" />
+        <state relative-caret-position="240">
+          <caret line="21" column="9" selection-start-line="21" selection-start-column="9" selection-end-line="21" selection-end-column="9" />
+        </state>
+      </provider>
+    </entry>
+    <entry file="file://$PROJECT_DIR$/src/semaphore/ValetQueue.java">
+      <provider selected="true" editor-type-id="text-editor">
+        <state relative-caret-position="135">
+          <caret line="11" lean-forward="true" selection-start-line="11" selection-end-line="11" />
         </state>
       </provider>
     </entry>
@@ -374,27 +380,10 @@
         </state>
       </provider>
     </entry>
-    <entry file="file://$PROJECT_DIR$/src/explicit/Main.java">
+    <entry file="file://$PROJECT_DIR$/src/semaphore/Main.java">
       <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="225">
-          <caret line="15" lean-forward="true" selection-start-line="15" selection-end-line="15" />
-          <folding>
-            <element signature="imports" expanded="true" />
-          </folding>
-        </state>
-      </provider>
-    </entry>
-    <entry file="jar:///Library/Java/JavaVirtualMachines/openjdk-12.0.1.jdk/Contents/Home/lib/src.zip!/java.base/java/util/concurrent/locks/ReentrantLock.java">
-      <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="200">
-          <caret line="148" column="22" selection-start-line="148" selection-start-column="22" selection-end-line="148" selection-end-column="22" />
-        </state>
-      </provider>
-    </entry>
-    <entry file="file://$PROJECT_DIR$/src/explicit/ExplicitValetQueue.java">
-      <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="70">
-          <caret line="36" column="62" selection-start-line="36" selection-start-column="62" selection-end-line="36" selection-end-column="62" />
+        <state relative-caret-position="135">
+          <caret line="9" column="43" selection-start-line="9" selection-start-column="43" selection-end-line="9" selection-end-column="43" />
         </state>
       </provider>
     </entry>
diff --git a/hw1/Ex2/src/explicit/ExplicitValetQueue.java b/hw1/Ex2/src/explicit/ExplicitValetQueue.java
index 598be1f..e22fb33 100644
--- a/hw1/Ex2/src/explicit/ExplicitValetQueue.java
+++ b/hw1/Ex2/src/explicit/ExplicitValetQueue.java
@@ -14,11 +14,17 @@ public class ExplicitValetQueue implements Queue<Car> {
 	private final int queueMaxSize;
 	private final ReentrantLock lock;
 	private final Condition full, empty;
+	private int firstFree = 0, firstFull = 0, nElements = 0;
 
 
 	public ExplicitValetQueue(int queueMaxSize) {
 		this.queueMaxSize = queueMaxSize;
 		waitingCars = new ArrayList<>(this.queueMaxSize);
+
+		for (int i = 0; i < queueMaxSize; i++) {
+			waitingCars.add(null);
+		}
+
 		lock = new ReentrantLock();
 		full = lock.newCondition();
 		empty = lock.newCondition();
@@ -28,11 +34,13 @@ public class ExplicitValetQueue implements Queue<Car> {
 	public void put(Car element) throws InterruptedException {
 		lock.lock();
 		try {
-			while (waitingCars.size() >= this.queueMaxSize) {
+			while (nElements == this.queueMaxSize) {
 				full.await();
 			}
 
-			waitingCars.add(element);
+			waitingCars.set(firstFree, element);
+			firstFree = (firstFree + 1) % queueMaxSize;
+			nElements++;
 			System.out.println("Car with plate " + element.getPlate() + " in queue");
 			System.out.println("Now waiting: " + waitingCars);
 
@@ -47,11 +55,15 @@ public class ExplicitValetQueue implements Queue<Car> {
 		final Car c;
 		lock.lock();
 		try {
-			while (waitingCars.isEmpty()) {
+			while (nElements == 0) {
 				empty.await();
 			}
 
-			c = waitingCars.remove(waitingCars.size() - 1);
+			c = waitingCars.get(this.firstFull);
+			waitingCars.set(this.firstFull, null);
+			firstFull = (firstFull + 1) % queueMaxSize;
+			nElements--;
+
 			System.out.println("Car with plate " + c.getPlate() + " will be parked now");
 			System.out.println("Now waiting: " + waitingCars);
 
diff --git a/hw1/Ex2/src/implicit/ImplicitValetQueue.java b/hw1/Ex2/src/implicit/ImplicitValetQueue.java
index e9534e0..d148e6e 100644
--- a/hw1/Ex2/src/implicit/ImplicitValetQueue.java
+++ b/hw1/Ex2/src/implicit/ImplicitValetQueue.java
@@ -10,19 +10,27 @@ import java.util.concurrent.Semaphore;
 public class ImplicitValetQueue implements Queue<Car> {
 	private final List<Car> waitingCars;
 	private final int queueMaxSize;
+	private int firstFree = 0, firstFull = 0, nElements = 0;
+
 
 	public ImplicitValetQueue(int queueMaxSize) {
 		this.queueMaxSize = queueMaxSize;
 		waitingCars = new ArrayList<>(this.queueMaxSize);
+
+		for (int i = 0; i < queueMaxSize; i++) {
+			waitingCars.add(null);
+		}
 	}
 
 	@Override
 	public synchronized void put(Car element) throws InterruptedException {
-		while (waitingCars.size() >= queueMaxSize) {
+		while (nElements == queueMaxSize) {
 			wait();
 		}
 
-		waitingCars.add(element);
+		waitingCars.set(firstFree, element);
+		firstFree = (firstFree + 1) % queueMaxSize;
+		nElements++;
 		System.out.println("Car with plate " + element.getPlate() + " in queue");
 		System.out.println("Now waiting: " + waitingCars);
 		notifyAll();
@@ -30,10 +38,14 @@ public class ImplicitValetQueue implements Queue<Car> {
 
 	@Override
 	public synchronized Car take() throws InterruptedException {
-		while (waitingCars.isEmpty()) {
+		while (nElements == 0) {
 			wait();
 		}
-		Car c = waitingCars.remove(waitingCars.size() - 1);
+		final Car c = waitingCars.get(this.firstFull);
+		waitingCars.set(this.firstFull, null);
+		firstFull = (firstFull + 1) % queueMaxSize;
+		nElements--;
+
 		System.out.println("Car with plate " + c.getPlate() + " will be parked now");
 		System.out.println("Now waiting: " + waitingCars);
 		notifyAll();
diff --git a/hw1/Ex2/src/semaphore/ValetQueue.java b/hw1/Ex2/src/semaphore/ValetQueue.java
index 5cf9b23..c0900a7 100644
--- a/hw1/Ex2/src/semaphore/ValetQueue.java
+++ b/hw1/Ex2/src/semaphore/ValetQueue.java
@@ -8,10 +8,16 @@ public class ValetQueue implements Queue<Car> {
 	private final List<Car> waitingCars;
 	private final int queueMaxSize;
 	private final Semaphore full, empty, mutex;
+	private int firstFree = 0, firstFull = 0;
 
 	public ValetQueue(int queueMaxSize) {
 		this.queueMaxSize = queueMaxSize;
 		waitingCars = new ArrayList<>(this.queueMaxSize);
+
+		for (int i = 0; i < queueMaxSize; i++) {
+			waitingCars.add(null);
+		}
+
 		empty = new Semaphore (this.queueMaxSize);
 		full = new Semaphore(0);
 		mutex = new Semaphore(1);
@@ -21,7 +27,8 @@ public class ValetQueue implements Queue<Car> {
 	public void put(Car element) throws InterruptedException {
 		empty.acquire();
 		mutex.acquire();
-		waitingCars.add(element);
+		waitingCars.set(firstFree, element);
+		firstFree = (firstFree + 1) % queueMaxSize;
 		System.out.println("Car with plate " + element.getPlate() + " in queue");
 		System.out.println("Now waiting: " + waitingCars);
 		mutex.release();
@@ -33,7 +40,9 @@ public class ValetQueue implements Queue<Car> {
 		final Car c;
 		full.acquire();
 		mutex.acquire();
-		c = waitingCars.remove(waitingCars.size() - 1);
+		c = waitingCars.get(this.firstFull);
+		waitingCars.set(this.firstFull, null);
+		firstFull = (firstFull + 1) % queueMaxSize;
 		System.out.println("Car with plate " + c.getPlate() + " will be parked now");
 		System.out.println("Now waiting: " + waitingCars);
 		mutex.release();