decimal to binary/octa/hexadecimal conversion

Here decimal to binary/octa/hexa decimal conversions are shown.

Algorithm is simple provided we should make use of the stack (stack implementation) to put the coefficients.

public class DecimalConversion {
	TNStack st = new TNStack(30);
	private static HashMap<Integer, String> hm = new HashMap<Integer, String>();
	
	/**
	 * converts number to given base
	 * @param number
	 * @param base
	 */
	public void decimalToXXXConversion(int number, int base) {
		System.out.println("Number "+number+" in base "+base+" is: ");
		while(number>0) {
			st.push(number%base);
			number = number/base;
		}
		
		while(!st.isEmpty()) {
			int n = st.pop();
			if(n>9) {
				String str = hm.get(n);
				System.out.print(str);
			} else {
				System.out.print(n);
			}
		}
		System.out.println();
	}
	
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		DecimalConversion dc = new DecimalConversion();
	
		// decimal to binary conversion
		dc.decimalToXXXConversion(100, 2);

		// decimal to octal conversion
		dc.decimalToXXXConversion(100, 8);
				
		// decimal to hexadecimal conversion
		hm.put(10, "A");
		hm.put(11, "B");
		hm.put(12, "C");
		hm.put(13, "D");
		hm.put(14, "E");
		hm.put(15, "F");
		dc.decimalToXXXConversion(10012, 16);	
	}
}

Output:
Number 100 in base 2 is:
1100100
Number 100 in base 8 is:
144
Number 10012 in base 16 is:
271C

Queue implementation in Java

Queues operate in FIFO model.

Queues are also used in various other data structures, some of them are

  • searching graphs
  • printer queues in our machines
  • keystroke data that is typed onto the keyboard

Efficiency of queue is that it performs insert and remove operations in O(1) complexity.

package algorithm.queue;

/**
 * @author ntallapa
 *
 */
public class TNQueue {
	private int size;
	private int[] queueArr;
	private int front = -1;
	private int rear = -1;
	private int totalItems;

	public TNQueue(int s) {
		size = s;
		queueArr = new int[s];
	}

	public void insert(int i) {
		rear++;
		System.out.println("Inserting "+i);
		queueArr[rear] = i;
		totalItems++;
	}

	public int remove() {
		front++;
		totalItems--;
		System.out.println("Removing "+queueArr[front]);
		return queueArr[front];
	}

	public boolean isFull() {
		return (totalItems == size);
	}

	public boolean isEmpty() {
		return (totalItems == 0);
	}
}

package algorithm.queue;
/**
 * @author ntallapa
 *
 */
public class TNQueueClient {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		TNQueue tnq = new TNQueue(3);
		if(!tnq.isFull())
			tnq.insert(1);
		if(!tnq.isFull())
			tnq.insert(2);
		if(!tnq.isFull())
			tnq.insert(3);
		if(!tnq.isFull())
			tnq.insert(4);
		else
			System.out.println("Queue is full, cannot insert element");

		if(!tnq.isEmpty())
			tnq.remove();
		if(!tnq.isEmpty())
			tnq.remove();
		if(!tnq.isEmpty())
			tnq.remove();
		if(!tnq.isEmpty())
			tnq.remove();
		else
			System.out.println("Queue is empty, cannot remove element");
	}
}

Output:
Inserting 1
Inserting 2
Inserting 3
Queue is full, cannot insert element
Removing 1
Removing 2
Removing 3
Queue is empty, cannot remove element

Stack implementation in Java

Stacks operate in LIFO model.

Stack plays vital role in many data structures, some of them are

  • in parsing arithmetic expressions
  • to help traverse nodes of binary tree
  • searching vertices of a graph
  • in java, every method’s return type and arguments are pushed on to a stack and when method returns they are popped off.

Efficiency of stack is that it performs push and pop operations in O(1) complexity.

package algorithm.stack;
/**
 * @author ntallapa
 *
 */
public class TNStack {
	private int size;
	private int[] stackArr;
	private int top = -1;
	
	public TNStack(int size) {
		this.size = size;
		stackArr = new int[size];
	}
	
	/**
	 * increment the ctr and push element into stack 
	 * @param i element to be pushed
	 */
	public void push(int i) {
		top++;
		System.out.println("Pushing "+i);
		stackArr[top] = i;
	}
	
	/**
	 * pop the element from stack and decrement the ctr 
	 * @return the popped element
	 */
	public int pop() {
		int i = stackArr[top];
		top--;
		System.out.println("Popping "+i);
		return i;
	}
	
	public int peek() {
		System.out.println("Peek "+stackArr[top]);
		return stackArr[top];
	}
	
	public boolean isFull() {
		return (top == size-1);
	}
	
	public boolean isEmpty() {
		return (top == -1);
	}
}

package algorithm.stack;
/**
 * @author ntallapa
 *
 */
public class TNStackClient {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		TNStack tns = new TNStack(3);
		// push some elements
		if(!tns.isFull())
			tns.push(4);
		if(!tns.isFull())
			tns.push(5);
		if(!tns.isFull())
			tns.push(3);
		if(!tns.isFull())
			tns.push(6);
		else 
			System.out.println("Stack is full, cannot push element");
		
		// pop some elements
		if(!tns.isEmpty())
			tns.pop();
		if(!tns.isEmpty())
			tns.pop();
		if(!tns.isEmpty())
			tns.pop();
		if(!tns.isEmpty())
			tns.pop();
		else 
			System.out.println("Stack is empty, cannot pop element");
		
		//reinsert to verify peek method
		if(!tns.isFull())
			tns.push(6);
		
		// peek couple of times; result should be same
		tns.peek();
		tns.peek();
	}
}

Output:
Pushing 4
Pushing 5
Pushing 3
Stack is full, cannot push element
Popping 3
Popping 5
Popping 4
Stack is empty, cannot pop element
Pushing 6
Peek 6
Peek 6

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