feat: move everything to single folder

cs2030s/Lab1/Queue.java

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+/**
+ * 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 + "]";
+  }
+}