feat: update structure

2024-01-22 14:27:40 +08:00
parent 7836c9185c
commit 3544a28a2e
559 changed files with 120846 additions and 4102 deletions
--- a/cs2030s/labs/Lab1/Array.java
+++ b/cs2030s/labs/Lab1/Array.java
@@ -0,0 +1,53 @@
+/**
+ * The Array for CS2030S
+ *
+ * @author Yadunand Prem
+ * @version CS2030S AY21/22 Semester 2
+ */
+
+class Array<T extends Comparable<T>> {
+  private T[] array;
+
+  public Array(int size) {
+    // The only way to add values to `array` is via set(), and we can only put
+    // objects of type T via that method. Thus, it is safe to cast Comparable[]
+    // to T[].
+    @SuppressWarnings("unchecked")
+    T[] temp = (T[]) new Comparable[size];
+    this.array = temp;
+  }
+
+  public void set(int index, T item) {
+    this.array[index] = item;
+  }
+
+  public T get(int index) {
+    return this.array[index];
+  }
+
+  public T min() {
+    T result = this.array[0];
+    for (T i : this.array) {
+      if (i.compareTo(result) < 0) {
+        result = i;
+      }
+    }
+    return result;
+  }
+
+  public int length() {
+    return this.array.length;
+  }
+
+  @Override
+  public String toString() {
+    StringBuilder s = new StringBuilder("[ ");
+    for (int i = 0; i < array.length; i++) {
+      s.append(i + ":" + array[i]);
+      if (i != array.length - 1) {
+        s.append(", ");
+      }
+    }
+    return s.append(" ]").toString();
+  }
+}
--- a/cs2030s/labs/Lab1/ArrayTest.java
+++ b/cs2030s/labs/Lab1/ArrayTest.java
@@ -0,0 +1,64 @@
+class ArrayTest {
+  public static void main(String[] args) {
+    CS2030STest i = new CS2030STest();
+
+    Array<Integer> a = new Array<Integer>(4);
+    i.expect("initializing an empty array",
+        a.toString(), "[ 0:null, 1:null, 2:null, 3:null ]");
+    a.set(0, 3);
+    i.expect("set element 0 to 3",
+        a.toString(), "[ 0:3, 1:null, 2:null, 3:null ]");
+    a.set(1, 4);
+    i.expect("set element 1 to 4",
+        a.toString(), "[ 0:3, 1:4, 2:null, 3:null ]");
+    a.set(2, 1);
+    i.expect("set element 2 to 1",
+        a.toString(), "[ 0:3, 1:4, 2:1, 3:null ]");
+    a.set(3, 6);
+    i.expect("set element 3 to 6",
+        a.toString(), "[ 0:3, 1:4, 2:1, 3:6 ]");
+    i.expect("get element 0",
+        a.get(0), 3);
+    i.expect("get element 1",
+        a.get(1), 4);
+    i.expect("get element 2",
+        a.get(2), 1);
+    i.expect("get element 3",
+        a.get(3), 6);
+
+    i.expect("smallest element is 1",
+        a.min(), 1);
+    i.expect("a.min() does not change the array",
+        a.toString(), "[ 0:3, 1:4, 2:1, 3:6 ]");
+    a.set(2, 9);
+    i.expect("update element 2 to 9",
+        a.toString(), "[ 0:3, 1:4, 2:9, 3:6 ]");
+    i.expect("smallest element is now 3",
+        a.min(), 3);
+
+    i.expectCompile("cannot put a non-integer into an array of integer",
+        "new Array<Integer>(4).set(0, false)", false);
+
+    i.expectCompile("cannot get a non-integer from an array of integer",
+        "String s = new Array<Integer>(4).get(0)", false);
+
+    i.expectCompile("cannot create an array of non-comparable element", 
+        "class A {} Array<A> a;", false);
+
+    i.expectCompile("cannot create an array of comparable element (but not to itself)", 
+        "class A implements Comparable<Long> {" +
+        "  public int compareTo(Long i) {" +
+        "    return 0; " +
+        "  }" +
+        "}" +
+        "Array<A> a;", false);
+
+    i.expectCompile("can create an array of comparable element (to itself)", 
+        "class A implements Comparable<A> {" +
+        "  public int compareTo(A i) {" +
+        "    return 0; " +
+        "  }" +
+        "}" +
+        "Array<A> a;", true);
+  }
+}
--- a/cs2030s/labs/Lab1/ArrivalEvent.java
+++ b/cs2030s/labs/Lab1/ArrivalEvent.java
@@ -0,0 +1,50 @@
+
+/**
+ * The ArrivalEvent is an Event which handles the arrival of a customer
+ * It decides whether a customer should go into queue or go to a counter
+ * It also allocates a counter to the customer. This event thus returns either a
+ * DepartureEvent or a ServiceBeginEvent
+ * 
+ * @author Yadunand Prem
+ * @version CS2030S AY22/23 Semester 2
+ */
+class ArrivalEvent extends Event {
+
+  private Customer customer;
+  private Shop shop;
+
+  public ArrivalEvent(Customer customer, Shop shop) {
+    super(customer.getArrivalTIme());
+    this.customer = customer;
+    this.shop = shop;
+  }
+
+  @Override
+  public Event[] simulate() {
+    ServiceCounter availableCounter = this.shop.getAvailableCounter();
+    // check if counters are available. If available, start service for that
+    // customer
+    if (availableCounter != null) {
+      return new Event[] {
+          new ServiceBeginEvent(this.getTime(), customer, shop, availableCounter) };
+    }
+    // if no counters available, check if queue slots avialable in counters
+    availableCounter = this.shop.findCounterWithQueue();
+    if (availableCounter != null) {
+      return new Event[] { 
+        new JoinCounterQueueEvent(this.getTime(), this.customer, availableCounter) 
+      };
+    }
+    // if shop queue isn't empty, join shop queue
+    if (!this.shop.isQueueFull()) {
+      return new Event[] { new JoinShopQueueEvent(customer, shop) };
+    }
+    return new Event[] { new DepartureEvent(this.getTime(), customer) };
+
+  }
+
+  @Override
+  public String toString() {
+    return String.format("%s: %s arrived %s", super.toString(), this.customer, this.shop);
+  }
+}
--- a/cs2030s/labs/Lab1/CS2030STest.java
+++ b/cs2030s/labs/Lab1/CS2030STest.java
@@ -0,0 +1,77 @@
+import java.net.URI;
+import java.util.List;
+import javax.tools.DiagnosticCollector;
+import javax.tools.SimpleJavaFileObject;
+import javax.tools.ToolProvider;
+
+class CS2030STest {
+
+  public static final String ANSI_RESET = "\u001B[0m";
+  public static final String ANSI_RED = "\u001B[31m";
+  public static final String ANSI_GREEN = "\u001B[32m";
+
+  /**
+   * Test if two objects are equals.
+   *
+   * @param test A description of the test.
+   * @param output The output from an expression.
+   * @param expect The expected output from that expression.
+   * @return this object.
+   */
+  public CS2030STest expect(String test, Object output, Object expect) {
+    System.out.print(test);
+    if ((expect == null && output == null) || output.equals(expect)) {
+      System.out.println(".. " + ANSI_GREEN + "ok" + ANSI_RESET);
+    } else {
+      System.out.println(".. " + ANSI_RED + "failed" + ANSI_RESET);
+      System.out.println("  expected: " + expect);
+      System.out.println("  got this: " + output);
+    }
+    return this;
+  }
+
+  /**
+   * Test if an expression compiles with/without error.
+   *
+   * @param test A description of the test.
+   * @param statement The java statement to compile
+   * @param success Whether the statement is expected to compile or not 
+   *     (true if yes; false otherwise)
+   * @return this object.
+   */
+  public CS2030STest expectCompile(String test, String statement, boolean success) {
+    System.out.print(test);
+
+    class JavaSourceFromString extends SimpleJavaFileObject {
+      final String code;
+
+      JavaSourceFromString(String code) {
+        super(URI.create("string:///TempClass.java"), Kind.SOURCE);
+        this.code = "class TempClass {void foo(){" +  code + ";}}";
+      }
+
+      @Override
+      public CharSequence getCharContent(boolean ignoreEncodingErrors) {
+        return code;
+      }
+    }
+
+    boolean noError = ToolProvider
+        .getSystemJavaCompiler()
+        .getTask(null, null, new DiagnosticCollector<>(), null, null, 
+            List.of(new JavaSourceFromString(statement)))
+        .call();
+
+    if (noError != success) {
+      System.out.println(".. " + ANSI_RED + "failed" + ANSI_RESET);
+      if (!success) {
+        System.out.println("  expected compilation error but it compiles fine.");
+      } else {
+        System.out.println("  expected the statement to compile without errors but it does not.");
+      }
+    } else {
+      System.out.println(".. " + ANSI_GREEN + "ok" + ANSI_RESET);
+    }
+    return this;
+  }
+}
--- a/cs2030s/labs/Lab1/Customer.java
+++ b/cs2030s/labs/Lab1/Customer.java
@@ -0,0 +1,34 @@
+/**
+ * This is a data class which holds information about the Customer.
+ * It has a incrementing counter for the customer id;
+ * 
+ * @author Yadunand Prem
+ * @version CS2030S AY22/23 Semester 2
+ */
+public class Customer {
+  private static int lastId = 0;
+
+  private final int id;
+  private final double serviceTime;
+  private final double arrivalTIme;
+
+  public Customer(double serviceTime, double arrivalTime) {
+    this.id = lastId++;
+    this.serviceTime = serviceTime;
+    this.arrivalTIme = arrivalTime;
+  }
+
+  public double getServiceTime() {
+    return this.serviceTime;
+  }
+
+  public double getArrivalTIme() {
+    return arrivalTIme;
+  }
+
+  @Override
+  public String toString() {
+    return "C" + id;
+  }
+
+}
--- a/cs2030s/labs/Lab1/DepartureEvent.java
+++ b/cs2030s/labs/Lab1/DepartureEvent.java
@@ -0,0 +1,28 @@
+/**
+ * The DepartureEvent is an Event which handles the end of a service.
+ * It handles allocating customers in queue to a counter.
+ * 
+ * @author Yadunand Prem
+ * @version CS2030S AY22/23 Semester 2
+ */
+class DepartureEvent extends Event {
+
+  private Customer customer;
+
+  public DepartureEvent(double time, Customer customer) {
+    super(time);
+    this.customer = customer;
+  }
+
+  @Override
+  public String toString() {
+    return String.format("%s: %s departed", super.toString(), this.customer);
+  }
+
+  @Override
+  public Event[] simulate() {
+    // when customer departs, check if there are customers in queue
+    return new Event[] {};
+  }
+
+}
--- a/cs2030s/labs/Lab1/Event.java
+++ b/cs2030s/labs/Lab1/Event.java
@@ -0,0 +1,72 @@
+/**
+ * The Event class is an abstract class that encapsulates a
+ * discrete event to be simulated. An event encapsulates the
+ * time the event occurs. A subclass of event _must_ override
+ * the simulate() method to implement the logic of the
+ * simulation when this event is simulated. The simulate method
+ * returns an array of events, which the simulator will then
+ * add to the event queue. Note that an event also implements
+ * the Comparable interface so that a PriorityQueue can
+ * arrange the events in the order of event time.
+ * 
+ * @author Yadunand Prem
+ * @version CS2030S AY22/23 Semester 2
+ */
+abstract class Event implements Comparable<Event> {
+  /** The time this event occurs in the simulation. */
+  private final double time;
+
+  /**
+   * Creates an event that occurs at the given time.
+   *
+   * @param time The time the event occurs.
+   */
+  public Event(double time) {
+    this.time = time;
+  }
+
+  /**
+   * Getter to return the time of this event.
+   *
+   * @return The time this event occurs.
+   */
+  public double getTime() {
+    return this.time;
+  }
+
+  /**
+   * Compare this event with a given event e.
+   *
+   * @param e The other event to compare to.
+   * @return 1 if this event occurs later than e;
+   *         0 if they occur the same time;
+   *         -1 if this event occurs earlier.
+   */
+  @Override
+  public int compareTo(Event e) {
+    if (this.time > e.time) {
+      return 1;
+    } else if (this.time == e.time) {
+      return 0;
+    } else {
+      return -1;
+    }
+  }
+
+  /**
+   * Return the string representation this event.
+   *
+   * @return A string consists of the time this event occurs.
+   */
+  @Override
+  public String toString() {
+    return String.format("%.3f", this.time);
+  }
+
+  /**
+   * Simulate this event.
+   *
+   * @return An array of new events to be scheduled by the simulator.
+   */
+  public abstract Event[] simulate();
+}
--- a/cs2030s/labs/Lab1/JoinCounterQueueEvent.java
+++ b/cs2030s/labs/Lab1/JoinCounterQueueEvent.java
@@ -0,0 +1,23 @@
+public class JoinCounterQueueEvent extends Event {
+  private Customer customer;
+  private ServiceCounter counter;
+
+  public JoinCounterQueueEvent(double time, Customer customer, ServiceCounter counter) {
+    super(time);
+    this.customer = customer;
+    this.counter = counter;
+  }
+
+  @Override
+  public Event[] simulate() {
+    this.counter.joinQueue(customer);
+    return new Event[] {};
+  }
+
+  @Override
+  public String toString() {
+    return String.format("%s: %s joined counter queue (at %s)",
+        super.toString(),
+        this.customer, this.counter);
+  }
+}
--- a/cs2030s/labs/Lab1/JoinShopQueueEvent.java
+++ b/cs2030s/labs/Lab1/JoinShopQueueEvent.java
@@ -0,0 +1,24 @@
+
+class JoinShopQueueEvent extends Event {
+  private Customer customer;
+  private Shop shop;
+
+  public JoinShopQueueEvent(Customer customer, Shop shop) {
+    super(customer.getArrivalTIme());
+    this.customer = customer;
+    this.shop = shop;
+  }
+
+  @Override
+  public Event[] simulate() {
+    this.shop.joinQueue(customer);
+    return new Event[] {};
+  }
+
+  @Override
+  public String toString() {
+    return String.format("%s: %s joined shop queue %s",
+        super.toString(),
+        this.customer, this.shop);
+  }
+}
--- a/cs2030s/labs/Lab1/Lab1.java
+++ b/cs2030s/labs/Lab1/Lab1.java
@@ -0,0 +1,26 @@
+import java.util.Scanner;
+
+/**
+ * The main class for CS2030S Lab 1.
+ *
+ * @author Yadunand Prem
+ * @version CS2030S AY22/23 Semester 2
+ */
+class Lab1 {
+  public static void main(String[] args) {
+
+    // Create a scanner to read from standard input.
+    Scanner sc = new Scanner(System.in);
+
+    // Create a simulation. The ShopSimulation
+    // constructor will read the simulation parameters
+    // and initial events using the scanner.
+    Simulation simulation = new ShopSimulation(sc);
+
+    // Create a new simulator and run the simulation
+    new Simulator(simulation).run();
+
+    // Clean up the scanner.
+    sc.close();
+  }
+}
--- a/cs2030s/labs/Lab1/Lab2.java
+++ b/cs2030s/labs/Lab1/Lab2.java
@@ -0,0 +1,26 @@
+import java.util.Scanner;
+
+/**
+ * The main class for CS2030S Lab 1.
+ *
+ * @author Wei Tsang
+ * @version CS2030S AY20/21 Semester 2
+ */
+class Lab2 {
+  public static void main(String[] args) {
+
+    // Create a scanner to read from standard input.
+    Scanner sc = new Scanner(System.in);
+
+    // Create a simulation.  The ShopSimulation 
+    // constructor will read the simulation parameters 
+    // and initial events using the scanner.
+    Simulation simulation = new ShopSimulation(sc);
+
+    // Create a new simulator and run the simulation
+    new Simulator(simulation).run();
+
+    // Clean up the scanner.
+    sc.close();
+  }
+}
--- a/cs2030s/labs/Lab1/Lab3.java
+++ b/cs2030s/labs/Lab1/Lab3.java
@@ -0,0 +1,26 @@
+import java.util.Scanner;
+
+/**
+ * The main class for CS2030S Lab 3.
+ *
+ * @author Wei Tsang
+ * @version CS2030S AY21/22 Semester 2
+ */
+class Lab3 {
+  public static void main(String[] args) {
+
+    // Create a scanner to read from standard input.
+    Scanner sc = new Scanner(System.in);
+
+    // Create a simulation.  The ShopSimulation 
+    // constructor will read the simulation parameters 
+    // and initial events using the scanner.
+    Simulation simulation = new ShopSimulation(sc);
+
+    // Create a new simulator and run the simulation
+    new Simulator(simulation).run();
+
+    // Clean up the scanner.
+    sc.close();
+  }
+}
--- a/cs2030s/labs/Lab1/Makefile
+++ b/cs2030s/labs/Lab1/Makefile
@@ -0,0 +1,17 @@
+CLASSES := $(wildcard *.java)
+
+default: classes
+
+lab1:
+	java Lab1
+
+lab2:
+	java Lab2
+
+classes: $(CLASSES:.java=.class)
+
+%.class : %.java
+	javac "$<"
+
+clean:
+	$(RM) *.class
--- a/cs2030s/labs/Lab1/Queue.java
+++ b/cs2030s/labs/Lab1/Queue.java
@@ -0,0 +1,125 @@
+/**
+ * The Queue class implements a simple FIFO data structure
+ * with limited capacity that can store any Object instances.
+ * Not to be confused with java.util.Queue.
+ *
+ * @author Yadunand Prem
+ * @version CS2030S AY21/22 Semester 2
+ */
+class Queue<T> {
+  /** An array to store the items in the queue. */
+  private T[] items;
+
+  /** Index of the first element in the queue. */
+  private int first;
+
+  /** Index of the last element in the queue. */
+  private int last;
+
+  /** Maximum size of the queue. */
+  private int maxSize;
+
+  /** Number of elements in the queue. */
+  private int len;
+
+  /**
+   * Constructor for a queue.
+   *
+   * @param size The maximum num of elements we can put in the queue.
+   */
+  public Queue(int size) {
+    this.maxSize = size;
+    // The only way to add values to `items` is via enq(), and we can only put
+    // objects of type T via that method. Thus, it is safe to cast Comparable[]
+    // to T[].
+    @SuppressWarnings("unchecked")
+    T[] temp = (T[]) new Object[size];
+    this.items = temp;
+    this.first = -1;
+    this.last = -1;
+    this.len = 0;
+  }
+
+  /**
+   * Add the object e into the queue.
+   *
+   * @param e The item to put in the queue.
+   * @return false if the queue is full; true if e is added successfully.
+   */
+  public boolean enq(T e) {
+    if (this.isFull()) {
+      return false;
+    }
+    if (this.isEmpty()) {
+      this.first = 0;
+      this.last = 0;
+    } else {
+      this.last = (this.last + 1) % this.maxSize;
+    }
+    this.items[last] = e;
+    this.len += 1;
+    return true;
+  }
+
+  /**
+   * Remove the object from the queue.
+   *
+   * @return null if the queue is empty; the object removed from the queue
+   *         otherwise.
+   */
+  public T deq() {
+    if (this.isEmpty()) {
+      return null;
+    }
+    T item = this.items[this.first];
+    this.first = (this.first + 1) % this.maxSize;
+    this.len -= 1;
+    return item;
+  }
+
+  /**
+   * Checks if the queue is full.
+   *
+   * @return true if the queue is full; false otherwise.
+   */
+  boolean isFull() {
+    return (this.len == this.maxSize);
+  }
+
+  /**
+   * Checks if the queue is empty.
+   *
+   * @return true if the queue is empty; false otherwise.
+   */
+  boolean isEmpty() {
+    return (this.len == 0);
+  }
+
+  /**
+   * Return the number of elements in the queue.
+   *
+   * @return The number of elements in the queue.
+   */
+  public int length() {
+    return this.len;
+  }
+
+  /**
+   * Returns the string representation of the queue.
+   * 
+   * @return A string consisting of the string representation of
+   *         every object in the queue.
+   */
+  @Override
+  public String toString() {
+    String str = "[ ";
+    int i = this.first;
+    int count = 0;
+    while (count < this.len) {
+      str += this.items[i] + " ";
+      i = (i + 1) % this.maxSize;
+      count++;
+    }
+    return str + "]";
+  }
+}
--- a/cs2030s/labs/Lab1/QueueTest.java
+++ b/cs2030s/labs/Lab1/QueueTest.java
@@ -0,0 +1,23 @@
+class QueueTest {
+
+  public static void main(String[] args) {
+    CS2030STest i = new CS2030STest();
+    Queue<Integer> q = new Queue<Integer>(2);
+    i.expect("insert 4 into a queue of integer",
+        q.enq(4), true);
+    i.expect("insert 8 into a queue of integer",
+        q.enq(8), true);
+    i.expect("insert 0 into a full queue",
+        q.enq(0), false);
+    i.expect("remove 4 from queue",
+        q.deq(), 4);
+    i.expect("remove 8 from queue",
+        q.deq(), 8);
+    i.expect("cannot deque anymore",
+        q.deq(), null);
+    i.expectCompile("cannot deque a non-integer from a queue of integer",
+        "String s = new Queue<Integer>(3).deq();", false);
+    i.expectCompile("cannot insert a non-integer into a queue of integer",
+        "new Queue<Integer>(3).enqueue(false);", false);
+  }
+}
--- a/cs2030s/labs/Lab1/ServiceBeginEvent.java
+++ b/cs2030s/labs/Lab1/ServiceBeginEvent.java
@@ -0,0 +1,34 @@
+/**
+ * The ServiceBeginEvent is an Event which handles the starting of a service.
+ * It handles occupying a counter and also generating a serviceEndEvent
+ * 
+ * @author Yadunand Prem
+ * @version CS2030S AY22/23 Semester 2
+ */
+class ServiceBeginEvent extends Event {
+
+  private ServiceCounter counter;
+  private Customer customer;
+  private Shop shop;
+
+  public ServiceBeginEvent(double time, Customer customer, Shop shop, ServiceCounter counter) {
+    super(time);
+    this.customer = customer;
+    this.shop = shop;
+    this.counter = counter;
+  }
+
+  @Override
+  public String toString() {
+    return super.toString()
+        + String.format(": %s service begin (by %s)", this.customer, this.counter);
+  }
+
+  @Override
+  public Event[] simulate() {
+    this.counter.occupy();
+    double endTime = this.getTime() + this.customer.getServiceTime();
+    return new Event[] {
+        new ServiceEndEvent(endTime, this.customer, this.shop, this.counter) };
+  }
+}
--- a/cs2030s/labs/Lab1/ServiceCounter.java
+++ b/cs2030s/labs/Lab1/ServiceCounter.java
@@ -0,0 +1,64 @@
+/**
+ * This is a data class which holds information about a counter. It has a
+ * incrementing counter for the conuter Id.
+ * 
+ * @author Yadunand Prem
+ * @version CS2030S AY22/23 Semester 2
+ */
+public class ServiceCounter implements Comparable<ServiceCounter> {
+  private static int lastId;
+
+  private final int id;
+  private boolean available;
+  private Queue<Customer> queue;
+
+  public boolean isAvailable() {
+    return available;
+  }
+
+  public void occupy() {
+    this.available = false;
+  }
+
+  public void free() {
+    this.available = true;
+  }
+
+  public boolean isQueueFull() {
+    return this.queue.isFull();
+  }
+
+  public boolean isQueueEmpty() {
+    return this.queue.isEmpty();
+  }
+
+  public void joinQueue(Customer customer) {
+    this.queue.enq(customer);
+  }
+
+  public Customer leaveQueue() {
+    return this.queue.deq();
+  }
+
+  public ServiceCounter(int queueSize) {
+    this.id = lastId++;
+    this.available = true;
+    this.queue = new Queue<Customer>(queueSize);
+  }
+
+  @Override
+  public String toString() {
+    return String.format("S%s %s", id, this.queue);
+  }
+
+  @Override
+  public int compareTo(ServiceCounter o) {
+    if (this.queue.length() < o.queue.length()) {
+      return -1;
+    }
+    if (this.id < o.id) {
+      return -1;
+    }
+    return 1;
+  }
+}
--- a/cs2030s/labs/Lab1/ServiceEndEvent.java
+++ b/cs2030s/labs/Lab1/ServiceEndEvent.java
@@ -0,0 +1,58 @@
+/**
+ * The ServiceEndEvent is an Event which handles the end of a service.
+ * It handles freeing the counter and also generating a departure event
+ * 
+ * @author Yadunand Prem
+ * @version CS2030S AY22/23 Semester 2
+ */
+class ServiceEndEvent extends Event {
+
+  private ServiceCounter counter;
+  private Customer customer;
+  private Shop shop;
+
+  public ServiceEndEvent(double time, Customer customer, Shop shop, ServiceCounter counter) {
+    super(time);
+    this.customer = customer;
+    this.shop = shop;
+    this.counter = counter;
+  }
+
+  @Override
+  public String toString() {
+    return super.toString()
+        + String.format(": %s service done (by %s)", this.customer, this.counter);
+  }
+
+  @Override
+  public Event[] simulate() {
+    // if there are customers in the counter queue, they will be serviced next.
+    // Customers in the shop queue will then be added to the counter queue
+    if (!this.counter.isQueueEmpty()) {
+      Customer serviceCustomer = this.counter.leaveQueue();
+
+      if (!this.shop.isQueueEmpty()) {
+        return new Event[] {
+            new DepartureEvent(this.getTime(), this.customer),
+            new ServiceBeginEvent(this.getTime(), serviceCustomer, this.shop, this.counter),
+            new JoinCounterQueueEvent(this.getTime(), this.shop.leaveQueue(), counter)
+        };
+      }
+      return new Event[] {
+          new DepartureEvent(this.getTime(), this.customer),
+          new ServiceBeginEvent(this.getTime(), serviceCustomer, this.shop, this.counter),
+      };
+    }
+    // There can also be the case where the counter queue may be empty but there are
+    // customers in the shop queue.
+    if (!this.shop.isQueueEmpty()) {
+      return new Event[] {
+          new DepartureEvent(this.getTime(), this.customer),
+          new ServiceBeginEvent(this.getTime(), this.shop.leaveQueue(), this.shop, this.counter),
+      };
+    }
+    // else there are no more customers in the queue, and the counter can be freed
+    this.counter.free();
+    return new Event[] { new DepartureEvent(this.getTime(), this.customer) };
+  }
+}
--- a/cs2030s/labs/Lab1/Shop.java
+++ b/cs2030s/labs/Lab1/Shop.java
@@ -0,0 +1,67 @@
+/**
+ * Shop is a data class which holds information about a shop.
+ * It stores the list of counters and the queue in which new customers can join.
+ * 
+ * @author Yadunand Prem
+ * @version CS2030S AY22/23 Semester 2
+ */
+public class Shop {
+  private Array<ServiceCounter> counters;
+  private Queue<Customer> queue;
+
+  public Shop(int numOfCounters, int shopQueueSize, int counterQueueSize) {
+    this.counters = new Array<ServiceCounter>(numOfCounters);
+    for (int i = 0; i < numOfCounters; i++) {
+      this.counters.set(i, new ServiceCounter(counterQueueSize));
+    }
+
+    this.queue = new Queue<Customer>(shopQueueSize);
+  }
+
+  /**
+   * getAvailableCounter returns the first available counter it finds.
+   * If there are none, returns null
+   * 
+   * @return the available counter or null if none found
+   */
+
+  public ServiceCounter getAvailableCounter() {
+    for (int i = 0; i < this.counters.length(); i++) {
+      ServiceCounter counter = this.counters.get(i);
+      if (counter.isAvailable()) {
+        return counter;
+      }
+    }
+    return null;
+  }
+
+  public boolean isQueueFull() {
+    return this.queue.isFull();
+  }
+
+  public boolean isQueueEmpty() {
+    return this.queue.isEmpty();
+  }
+
+  public void joinQueue(Customer customer) {
+    this.queue.enq(customer);
+  }
+
+  public Customer leaveQueue() {
+    return this.queue.deq();
+  }
+
+  public ServiceCounter findCounterWithQueue() {
+    ServiceCounter minCounter = this.counters.min();
+    if (!minCounter.isQueueFull()) {
+      return minCounter;
+    }
+    return null;
+  }
+
+  @Override
+  public String toString() {
+    return this.queue.toString();
+  }
+
+}
--- a/cs2030s/labs/Lab1/ShopSimulation.java
+++ b/cs2030s/labs/Lab1/ShopSimulation.java
@@ -0,0 +1,53 @@
+import java.util.Scanner;
+
+/**
+ * This class implements a shop simulation.
+ *
+ * @author Yadunand Prem
+ * @version CS2030S AY22/23 Semester 2
+ */
+class ShopSimulation extends Simulation {
+
+  /**
+   * The list of customer arrival events to populate
+   * the simulation with.
+   */
+  private Event[] initEvents;
+
+  /**
+   * Constructor for a shop simulation.
+   *
+   * @param sc A scanner to read the parameters from. The first
+   *           integer scanned is the number of customers; followed
+   *           by the number of service counters. Next is a
+   *           sequence of (arrival time, service time) pair, each
+   *           pair represents a customer.
+   */
+  public ShopSimulation(Scanner sc) {
+    initEvents = new Event[sc.nextInt()];
+    int numOfCounters = sc.nextInt();
+    int maxCounterQueueSize = sc.nextInt();
+    int maxShopQueueSize = sc.nextInt();
+
+    Shop shop = new Shop(numOfCounters, maxShopQueueSize, maxCounterQueueSize);
+
+    int id = 0;
+    while (sc.hasNextDouble()) {
+      double arrivalTime = sc.nextDouble();
+      double serviceTime = sc.nextDouble();
+      initEvents[id] = new ArrivalEvent(new Customer(serviceTime, arrivalTime), shop);
+      id += 1;
+    }
+  }
+
+  /**
+   * Retrieve an array of events to populate the
+   * simulator with.
+   *
+   * @return An array of events for the simulator.
+   */
+  @Override
+  public Event[] getInitialEvents() {
+    return initEvents;
+  }
+}
--- a/cs2030s/labs/Lab1/Simulation.java
+++ b/cs2030s/labs/Lab1/Simulation.java
@@ -0,0 +1,20 @@
+/**
+ * This class is a general abstract class that
+ * encapsulates a simulation. To implement a
+ * simulation, inherit from this class and implement
+ * the `getInitialEvents` method.
+ *
+ * @author Yadunand Prem
+ * @version CS2030S AY22/23 Semester 2
+ */
+abstract class Simulation {
+  /**
+   * An abstract method to return an array of events
+   * used to initialize the simulation.
+   *
+   * @return An array of initial events that the
+   *         simulator can use to kick-start the
+   *         simulation.
+   */
+  public abstract Event[] getInitialEvents();
+}
--- a/cs2030s/labs/Lab1/Simulator.java
+++ b/cs2030s/labs/Lab1/Simulator.java
@@ -0,0 +1,51 @@
+import java.util.PriorityQueue;
+
+/**
+ * This class implements a discrete event simulator.
+ * The simulator maintains a priority queue of events.
+ * It runs through the events and simulates each one until
+ * the queue is empty.
+ *
+ * @author Yadunand Prem
+ * @version CS2030S AY22/23 Semester 2
+ */
+public class Simulator {
+  /** The event queue. */
+  private final PriorityQueue<Event> events;
+
+  /**
+   * The constructor for a simulator. It takes in
+   * a simulation as an argument, and calls the
+   * getInitialEvents method of that simulation to
+   * initialize the event queue.
+   *
+   * @param simulation The simulation to simulate.
+   */
+  public Simulator(Simulation simulation) {
+    this.events = new PriorityQueue<Event>();
+    for (Event e : simulation.getInitialEvents()) {
+      this.events.add(e);
+    }
+  }
+
+  /**
+   * Run the simulation until no more events is in
+   * the queue. For each event in the queue (in
+   * increasing order of time), print out its string
+   * representation, then simulate it. If the
+   * simulation returns one or more events, add them
+   * to the queue, and repeat.
+   */
+  public void run() {
+    Event event = this.events.poll();
+    while (event != null) {
+      System.out.println(event);
+      Event[] newEvents = event.simulate();
+      for (Event e : newEvents) {
+        this.events.add(e);
+      }
+      event = this.events.poll();
+    }
+    return;
+  }
+}
--- a/cs2030s/labs/Lab1/inputs/Lab1.1.in
+++ b/cs2030s/labs/Lab1/inputs/Lab1.1.in
@@ -0,0 +1,4 @@
+3 1
+1.0 1.0
+3.0 1.0
+5.0 1.0
--- a/cs2030s/labs/Lab1/inputs/Lab1.2.in
+++ b/cs2030s/labs/Lab1/inputs/Lab1.2.in
@@ -0,0 +1,4 @@
+3 1 
+1.1 2.0
+2.2 2.0
+3.3 2.0
--- a/cs2030s/labs/Lab1/inputs/Lab1.3.in
+++ b/cs2030s/labs/Lab1/inputs/Lab1.3.in
@@ -0,0 +1,6 @@
+5 2
+1.0 1.0
+1.2 1.0
+1.4 1.0
+1.6 1.0
+2.1 1.0
--- a/cs2030s/labs/Lab1/inputs/Lab1.4.in
+++ b/cs2030s/labs/Lab1/inputs/Lab1.4.in
@@ -0,0 +1,5 @@
+4 2
+1.0 1.0
+1.1 1.0
+2.2 1.0
+2.3 1.0
--- a/cs2030s/labs/Lab1/inputs/Lab1.5.in
+++ b/cs2030s/labs/Lab1/inputs/Lab1.5.in
@@ -0,0 +1,4 @@
+3 2
+1.0 4
+2.1 1
+4.2 1
--- a/cs2030s/labs/Lab1/inputs/Lab2.1.in
+++ b/cs2030s/labs/Lab1/inputs/Lab2.1.in
@@ -0,0 +1,4 @@
+3 1 2
+1.0 1.0
+3.0 1.0
+5.0 1.0
--- a/cs2030s/labs/Lab1/inputs/Lab2.10.in
+++ b/cs2030s/labs/Lab1/inputs/Lab2.10.in
@@ -0,0 +1,6 @@
+5 2 2
+1.0 1.5
+1.2 1.0
+1.4 1.0
+1.6 1.0
+2.1 1.0
--- a/cs2030s/labs/Lab1/inputs/Lab2.2.in
+++ b/cs2030s/labs/Lab1/inputs/Lab2.2.in
@@ -0,0 +1,4 @@
+3 1 2
+1.1 2.0
+2.2 2.0
+3.3 2.0
--- a/cs2030s/labs/Lab1/inputs/Lab2.3.in
+++ b/cs2030s/labs/Lab1/inputs/Lab2.3.in
@@ -0,0 +1,7 @@
+6 1 2
+1.1 2
+1.2 2
+1.3 2
+1.4 2
+4.0 2
+5.0 2
--- a/cs2030s/labs/Lab1/inputs/Lab2.4.in
+++ b/cs2030s/labs/Lab1/inputs/Lab2.4.in
@@ -0,0 +1,7 @@
+6 1 3
+1.1 2
+1.2 2
+1.3 2
+1.4 2
+4.0 2
+5.0 2
--- a/cs2030s/labs/Lab1/inputs/Lab2.5.in
+++ b/cs2030s/labs/Lab1/inputs/Lab2.5.in
@@ -0,0 +1,5 @@
+4 2 1
+1.0 1.0
+1.1 1.0
+2.2 1.0
+2.3 1.0
--- a/cs2030s/labs/Lab1/inputs/Lab2.6.in
+++ b/cs2030s/labs/Lab1/inputs/Lab2.6.in
@@ -0,0 +1,5 @@
+4 2 2
+1.0 1.0
+1.1 1.0
+2.2 1.0
+2.3 1.0
--- a/cs2030s/labs/Lab1/inputs/Lab2.7.in
+++ b/cs2030s/labs/Lab1/inputs/Lab2.7.in
@@ -0,0 +1,4 @@
+3 2 1
+1.0 4
+2.1 1
+4.2 1
--- a/cs2030s/labs/Lab1/inputs/Lab2.8.in
+++ b/cs2030s/labs/Lab1/inputs/Lab2.8.in
@@ -0,0 +1,6 @@
+5 2 1
+1.0 1.0
+1.2 1.0
+1.4 1.0
+1.6 1.0
+2.1 1.0
--- a/cs2030s/labs/Lab1/inputs/Lab2.9.in
+++ b/cs2030s/labs/Lab1/inputs/Lab2.9.in
@@ -0,0 +1,6 @@
+5 2 2
+1.0 1.0
+1.2 1.0
+1.4 1.0
+1.6 1.0
+2.1 1.0
--- a/cs2030s/labs/Lab1/inputs/Lab3.1.in
+++ b/cs2030s/labs/Lab1/inputs/Lab3.1.in
@@ -0,0 +1,4 @@
+3 1 0 2
+1.0 1.0
+3.0 1.0
+5.0 1.0
--- a/cs2030s/labs/Lab1/inputs/Lab3.10.in
+++ b/cs2030s/labs/Lab1/inputs/Lab3.10.in
@@ -0,0 +1,6 @@
+5 2 0 2
+1.0 1.5
+1.2 1.0
+1.4 1.0
+1.6 1.0
+2.1 1.0
--- a/cs2030s/labs/Lab1/inputs/Lab3.11.in
+++ b/cs2030s/labs/Lab1/inputs/Lab3.11.in
@@ -0,0 +1,6 @@
+5 1 2 0
+1.0 1.0
+1.1 1.0
+1.2 1.0
+1.3 1.0
+1.4 1.0
--- a/cs2030s/labs/Lab1/inputs/Lab3.12.in
+++ b/cs2030s/labs/Lab1/inputs/Lab3.12.in
@@ -0,0 +1,12 @@
+11 3 3 0
+1.0 2
+1.1 1
+1.2 1
+1.3 1
+1.4 1
+1.5 2
+1.6 2
+1.7 2
+1.8 2
+1.9 2
+2.15 1
--- a/cs2030s/labs/Lab1/inputs/Lab3.13.in
+++ b/cs2030s/labs/Lab1/inputs/Lab3.13.in
@@ -0,0 +1,12 @@
+11 3 3 0
+1.0 2
+1.1 1
+1.2 1
+1.3 1
+1.4 1
+1.5 2
+1.6 2
+1.7 2
+1.8 2
+1.9 2
+2.25 1
--- a/cs2030s/labs/Lab1/inputs/Lab3.14.in
+++ b/cs2030s/labs/Lab1/inputs/Lab3.14.in
@@ -0,0 +1,13 @@
+12 3 2 2
+1.0 2
+1.1 2
+1.2 2
+1.3 2
+1.4 2
+1.5 2
+1.6 2
+1.7 2
+1.8 2
+1.9 2
+2.0 2
+2.1 2
--- a/cs2030s/labs/Lab1/inputs/Lab3.15.in
+++ b/cs2030s/labs/Lab1/inputs/Lab3.15.in
@@ -0,0 +1,13 @@
+12 3 2 3
+1.0 2
+1.1 3
+1.2 2
+1.3 3
+1.4 2
+1.5 3
+1.6 2
+1.7 3
+1.8 2
+1.9 3
+2.0 2
+2.1 3
--- a/cs2030s/labs/Lab1/inputs/Lab3.2.in
+++ b/cs2030s/labs/Lab1/inputs/Lab3.2.in
@@ -0,0 +1,4 @@
+3 1 0 2
+1.1 2.0
+2.2 2.0
+3.3 2.0
--- a/cs2030s/labs/Lab1/inputs/Lab3.3.in
+++ b/cs2030s/labs/Lab1/inputs/Lab3.3.in
@@ -0,0 +1,7 @@
+6 1 0 2
+1.1 2
+1.2 2
+1.3 2
+1.4 2
+4.0 2
+5.0 2
--- a/cs2030s/labs/Lab1/inputs/Lab3.4.in
+++ b/cs2030s/labs/Lab1/inputs/Lab3.4.in
@@ -0,0 +1,7 @@
+6 1 0 3
+1.1 2
+1.2 2
+1.3 2
+1.4 2
+4.0 2
+5.0 2
--- a/cs2030s/labs/Lab1/inputs/Lab3.5.in
+++ b/cs2030s/labs/Lab1/inputs/Lab3.5.in
@@ -0,0 +1,5 @@
+4 2 0 1
+1.0 1.0
+1.1 1.0
+2.2 1.0
+2.3 1.0
--- a/cs2030s/labs/Lab1/inputs/Lab3.6.in
+++ b/cs2030s/labs/Lab1/inputs/Lab3.6.in
@@ -0,0 +1,5 @@
+4 2 0 2
+1.0 1.0
+1.1 1.0
+2.2 1.0
+2.3 1.0
--- a/cs2030s/labs/Lab1/inputs/Lab3.7.in
+++ b/cs2030s/labs/Lab1/inputs/Lab3.7.in
@@ -0,0 +1,4 @@
+3 2 0 1
+1.0 4
+2.1 1
+4.2 1
--- a/cs2030s/labs/Lab1/inputs/Lab3.8.in
+++ b/cs2030s/labs/Lab1/inputs/Lab3.8.in
@@ -0,0 +1,6 @@
+5 2 0 1
+1.0 1.0
+1.2 1.0
+1.4 1.0
+1.6 1.0
+2.1 1.0
--- a/cs2030s/labs/Lab1/inputs/Lab3.9.in
+++ b/cs2030s/labs/Lab1/inputs/Lab3.9.in
@@ -0,0 +1,6 @@
+5 2 0 2
+1.0 1.0
+1.2 1.0
+1.4 1.0
+1.6 1.0
+2.1 1.0
--- a/cs2030s/labs/Lab1/test.sh
+++ b/cs2030s/labs/Lab1/test.sh
@@ -0,0 +1,77 @@
+#!/bin/bash
+set -o nounset
+function control_c() {
+	if [ -e $out ]
+		then
+			rm -f $out
+		fi
+}
+
+trap control_c INT
+
+if [ $# -ne 1 ]
+then
+	echo "usage: $0 <main class>"
+	exit 1
+fi
+
+PROG=$1
+if [ ! -e $PROG.class ]
+then
+	echo "$PROG.class does not exist.  Have you compiled it with make or javac?"
+	exit 1
+fi
+
+num_failed=0
+i=1
+while true
+do
+	if [ -e inputs/$PROG.$i.in ]
+	then
+		if [ $(uname) == "Darwin" ]
+		then
+			out=$(mktemp -t $PROG)
+		else
+			out=$(mktemp --suffix=$PROG)
+		fi
+		java $PROG < inputs/$PROG.$i.in  > $out
+		status="$?"
+		if [ "$status" -ne "0" ]
+		then
+			echo "$PROG: return non-zero status $status for test case $i"
+			# cat inputs/$PROG.$i.in
+			num_failed=$((num_failed + 1))
+		else 
+			if [ -e $out ] 
+			then
+				if [ `diff -bB $out outputs/$PROG.$i.out | wc -l` -ne 0 ] 
+				then
+					echo "$PROG test $i: failed"
+					#cat inputs/$PROG.$i.in
+					num_failed=$((num_failed + 1))
+				else
+					echo "$PROG test $i: passed"
+				fi
+				rm -f $out
+			else
+				echo "$PROG: cannot find output file. Execution interrupted?"
+				num_failed=$((num_failed + 1))
+			fi
+		fi
+		i=$((i + 1))
+	else
+		break
+	fi
+done
+
+if [ $i -eq 1 ] 
+then
+	echo "$PROG: no test cases found 🤷"
+elif [ $num_failed -eq 0 ] 
+then
+	echo "$PROG: passed everything 🎉"
+fi
+# Run style checker
+#java -jar ~cs2030s/bin/checkstyle.jar -c ~cs2030s/bin/cs2030_checks.xml *.java 
+java -jar ./checkstyle.jar -c ./cs2030_checks.xml *.java 
+# vim:noexpandtab:sw=4:ts=4