Important Notice:

Practice-It will be discontinued as of November 1st, 2024. After this date, the website will remain online for a transitional period, but login will be restricted to University of Washington NetID authentication. This marks the next phase towards the platform's full retirement. Thank you for your use and support of the application over the years.

If you are looking for an alternative, a similar tool, CodeStepByStep, was developed independently by the original author of Practice-It, and is available at codestepbystep.com**

logo Practice-It logo

Main Page → Problems → Solve a Problem

BJP3 Exercise 12.19: countBinary

Language/Type: Java recursion recursive backtracking
Author: Marty Stepp (on 2013/04/01)

Write a method countBinary that accepts an integer n as a parameter and that prints all binary numbers that have n digits in ascending order, printing each value on a separate line. All n digits should be shown for all numbers, including leading zeros if necessary. You may assume that n is non-negative. If n is 0, a blank line of output should be produced. Do not use a loop in your solution; implement it recursively.

Call Output 
countBinary(1);
 
0
1

countBinary(2);
 
00
01
10
11

countBinary(3);
 
000
001
010
011
100
101
110
111

Hint: It may help to define a private helper method that accepts different parameters than the original method. In particular, consider building up a set of characters as a String for eventual printing.

Type your solution here:


This is a method problem. Write a Java method as described. Do not write a complete program or class; just the method(s) above.

You must log in before you can solve this problem.


Log In

If you do not understand how to solve a problem or why your solution doesn't work, please contact your TA or instructor.
If something seems wrong with the site (errors, slow performance, incorrect problems/tests, etc.), please

Is there a problem? Contact a site administrator.