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Others/QueueUsingTwoStacks.java

@@ -5,156 +5,146 @@ import java.util.Stack;
 /**
  * This implements Queue using two Stacks.
  *
- * Big O Runtime:
- *      insert(): O(1)
- *      remove(): O(1) amortized
- *      isEmpty(): O(1)
+ * <p>Big O Runtime: insert(): O(1) remove(): O(1) amortized isEmpty(): O(1)
  *
- * A queue data structure functions the same as a real world queue.
- * The elements that are added first are the first to be removed.
- * New elements are added to the back/rear of the queue.
+ * <p>A queue data structure functions the same as a real world queue. The elements that are added
+ * first are the first to be removed. New elements are added to the back/rear of the queue.
  *
  * @author sahilb2 (https://www.github.com/sahilb2)
- *
  */
 class QueueWithStack {
 
-    // Stack to keep track of elements inserted into the queue
-    private Stack inStack;
-    // Stack to keep track of elements to be removed next in queue
-    private Stack outStack;
+  // Stack to keep track of elements inserted into the queue
+  private Stack inStack;
+  // Stack to keep track of elements to be removed next in queue
+  private Stack outStack;
 
-    /**
-	 * Constructor
-	 */
-    public QueueWithStack() {
-        this.inStack = new Stack();
-        this.outStack = new Stack();
+  /** Constructor */
+  public QueueWithStack() {
+    this.inStack = new Stack();
+    this.outStack = new Stack();
+  }
+
+  /**
+   * Inserts an element at the rear of the queue
+   *
+   * @param x element to be added
+   */
+  public void insert(Object x) {
+    // Insert element into inStack
+    this.inStack.push(x);
+  }
+
+  /**
+   * Remove an element from the front of the queue
+   *
+   * @return the new front of the queue
+   */
+  public Object remove() {
+    if (this.outStack.isEmpty()) {
+      // Move all elements from inStack to outStack (preserving the order)
+      while (!this.inStack.isEmpty()) {
+        this.outStack.push(this.inStack.pop());
+      }
     }
+    return this.outStack.pop();
+  }
 
-    /**
-     * Inserts an element at the rear of the queue
-     *
-     * @param x element to be added
-     */
-    public void insert(Object x) {
-        // Insert element into inStack
-        this.inStack.push(x);
+  /**
+   * Peek at the element from the front of the queue
+   *
+   * @return the front element of the queue
+   */
+  public Object peekFront() {
+    if (this.outStack.isEmpty()) {
+      // Move all elements from inStack to outStack (preserving the order)
+      while (!this.inStack.isEmpty()) {
+        this.outStack.push(this.inStack.pop());
+      }
     }
+    return this.outStack.peek();
+  }
 
-    /**
-     * Remove an element from the front of the queue
-     *
-     * @return the new front of the queue
-     */
-    public Object remove() {
-        if(this.outStack.isEmpty()) {
-            // Move all elements from inStack to outStack (preserving the order)
-            while(!this.inStack.isEmpty()) {
-                this.outStack.push( this.inStack.pop() );
-            }
-        }
-        return this.outStack.pop();
-    }
-
-    /**
-     * Peek at the element from the front of the queue
-     *
-     * @return the front element of the queue
-     */
-    public Object peekFront() {
-        if(this.outStack.isEmpty()) {
-            // Move all elements from inStack to outStack (preserving the order)
-            while(!this.inStack.isEmpty()) {
-                this.outStack.push( this.inStack.pop() );
-            }
-        }
-        return this.outStack.peek();
-    }
-
-    /**
-     * Peek at the element from the back of the queue
-     *
-     * @return the back element of the queue
-     */
-    public Object peekBack() {
-        return this.inStack.peek();
-    }
-
-    /**
-     * Returns true if the queue is empty
-     *
-     * @return true if the queue is empty
-     */
-    public boolean isEmpty() {
-        return (this.inStack.isEmpty() && this.outStack.isEmpty());
-    }
+  /**
+   * Peek at the element from the back of the queue
+   *
+   * @return the back element of the queue
+   */
+  public Object peekBack() {
+    return this.inStack.peek();
+  }
 
+  /**
+   * Returns true if the queue is empty
+   *
+   * @return true if the queue is empty
+   */
+  public boolean isEmpty() {
+    return (this.inStack.isEmpty() && this.outStack.isEmpty());
+  }
 }
 
 /**
  * This class is the example for the Queue class
  *
  * @author sahilb2 (https://www.github.com/sahilb2)
- *
  */
 public class QueueUsingTwoStacks {
 
-    /**
-     * Main method
-     *
-     * @param args Command line arguments
-     */
-    public static void main(String args[]){
-        QueueWithStack myQueue = new QueueWithStack();
-        myQueue.insert(1);
-        System.out.println(myQueue.peekBack()); //Will print 1
-        // instack: [(top) 1]
-        // outStack: []
-        myQueue.insert(2);
-        System.out.println(myQueue.peekBack()); //Will print 2
-        // instack: [(top) 2, 1]
-        // outStack: []
-        myQueue.insert(3);
-        System.out.println(myQueue.peekBack()); //Will print 3
-        // instack: [(top) 3, 2, 1]
-        // outStack: []
-        myQueue.insert(4);
-        System.out.println(myQueue.peekBack()); //Will print 4
-        // instack: [(top) 4, 3, 2, 1]
-        // outStack: []
+  /**
+   * Main method
+   *
+   * @param args Command line arguments
+   */
+  public static void main(String args[]) {
+    QueueWithStack myQueue = new QueueWithStack();
+    myQueue.insert(1);
+    System.out.println(myQueue.peekBack()); // Will print 1
+    // instack: [(top) 1]
+    // outStack: []
+    myQueue.insert(2);
+    System.out.println(myQueue.peekBack()); // Will print 2
+    // instack: [(top) 2, 1]
+    // outStack: []
+    myQueue.insert(3);
+    System.out.println(myQueue.peekBack()); // Will print 3
+    // instack: [(top) 3, 2, 1]
+    // outStack: []
+    myQueue.insert(4);
+    System.out.println(myQueue.peekBack()); // Will print 4
+    // instack: [(top) 4, 3, 2, 1]
+    // outStack: []
 
-        System.out.println(myQueue.isEmpty()); //Will print false
+    System.out.println(myQueue.isEmpty()); // Will print false
 
-        System.out.println(myQueue.remove()); //Will print 1
-        System.out.println(myQueue.peekBack()); //Will print NULL
-        // instack: []
-        // outStack: [(top) 2, 3, 4]
+    System.out.println(myQueue.remove()); // Will print 1
+    System.out.println(myQueue.peekBack()); // Will print NULL
+    // instack: []
+    // outStack: [(top) 2, 3, 4]
 
-        myQueue.insert(5);
-        System.out.println(myQueue.peekFront()); //Will print 2
-        // instack: [(top) 5]
-        // outStack: [(top) 2, 3, 4]
+    myQueue.insert(5);
+    System.out.println(myQueue.peekFront()); // Will print 2
+    // instack: [(top) 5]
+    // outStack: [(top) 2, 3, 4]
 
-        myQueue.remove();
-        System.out.println(myQueue.peekFront()); //Will print 3
-        // instack: [(top) 5]
-        // outStack: [(top) 3, 4]
-        myQueue.remove();
-        System.out.println(myQueue.peekFront()); //Will print 4
-        // instack: [(top) 5]
-        // outStack: [(top) 4]
-        myQueue.remove();
-        // instack: [(top) 5]
-        // outStack: []
-        System.out.println(myQueue.peekFront()); //Will print 5
-        // instack: []
-        // outStack: [(top) 5]
-        myQueue.remove();
-        // instack: []
-        // outStack: []
+    myQueue.remove();
+    System.out.println(myQueue.peekFront()); // Will print 3
+    // instack: [(top) 5]
+    // outStack: [(top) 3, 4]
+    myQueue.remove();
+    System.out.println(myQueue.peekFront()); // Will print 4
+    // instack: [(top) 5]
+    // outStack: [(top) 4]
+    myQueue.remove();
+    // instack: [(top) 5]
+    // outStack: []
+    System.out.println(myQueue.peekFront()); // Will print 5
+    // instack: []
+    // outStack: [(top) 5]
+    myQueue.remove();
+    // instack: []
+    // outStack: []
 
-        System.out.println(myQueue.isEmpty()); //Will print true
-
-    }
+    System.out.println(myQueue.isEmpty()); // Will print true
+  }
 }