Duck number in Java

In this tutorial, we will understand what is meant by the Duck number in Java and understand it through Java Program.

In programming, a duck number is a positive number that contains zeroes in it, but not at the beginning.

Example -

1. 101 is a duck number since it contains a zero in the middle.
2. 2345606 is a duck number since it contains a zero in the middle.
3. 30303 is a duck number since it contains a zero in the middle.
4. 0456037 is a duck number since it contains a zero not only in the beginning but also in the middle.
5. 01011 is a duck number since it contains a zero not only in the beginning but also in the middle.
6. 56770 is a duck number since it contains a zero at the end but not at the beginning.
7. 015110 is a duck number since it contains a zero not only in the beginning but also at the end.
8. 04567 is not a duck number since it contains a zero only at the beginning.
9. 0863 is not a duck number since it contains a zero only at the beginning.
10. 0875 is not a duck number since it contains a zero only at the beginning.

Algorithm:

1. Create a class named "Duck_Number".
2. Create a static method "isDuck" that takes a string parameter "num" and returns a boolean value. This method will check if the given number is a duck number or not.
3. In the "isDuck" method, initialize two variables "i" and "n" to 0 and the length of the string "num", respectively.
4. Using a while loop, drop the leading zeroes from the given number.
5. Using another while loop, check the remaining digits of the number.
6. If the first non-zero digit encountered is zero, then the number is a duck number. Return true.
7. If no zeroes are found in the remaining digits, then the number is not a duck number. Return false.
8. In the main method, create a Scanner object "sc" to read the input from the user.
9. Print a message asking the user to enter a number.
10. Read the input number as a string using the nextLine method of the Scanner object.
11. Call the "isDuck" method with the input number as the argument.
12. If the returned value is true, then print "It is a duck number".
13. If the returned value is false, then print "It is not a Duck number”.

Implementation:

File name: Duck_Number.java

// Java Program to check whether a
// number is Duck Number or not.


import java.io.*;
import java.util.*;
class Duck_Number {


	// function to check if
	// the entered number is duck number or not?
	static boolean isDuck(String num)
	{
		// dropping leading zeroes
		int i = 0, n = num.length();
		while (i < n && num.charAt(i) == '0')
			i++;


		// Check the left over digits
		while (i < n) {
			if (num.charAt(i) == '0')
				return true;
			i++;
		}


		return false;
	}


	// main Method
	public static void main(String args[]) throws IOException
	{
	    Scanner sc = new Scanner(System.in);  
	    System.out.println("Enter any no.:");
	    String num = sc.nextLine();
		if (isDuck(num))
			System.out.println("It is a duck number");
		else
			System.out.println("It is not a duck number");
	}
}

Output 1:

Output 2:

Output 3:

Output 4:

Complexity Analysis:

Time Complexity: O(n) where n is the length of the string.

Space Complexity: O (1)