For Java practice I started working on a method countBinary
that accepts an integer n
as a parameter that prints all binary numbers that have n
digits in ascending order, printing each value on a separate line. Assuming n is non-negative and greater than 0, some example outputs would look like this .
I am getting pretty much nowhere with this. I am able to write a program that finds all possible letter combinations of a String
and similar things, but I have been unable to make almost any progress with this specific problem using binary and integers.
Apparently the best way to go about this issue is by defining a helper method that accepts different parameters than the original method and by building up a set of characters as a String for eventual printing.
Important Note: I am NOT supposed to use for loops at all for this exercise.
Edit - Important Note: I need to have trailing 0's so that all outputs are the same length.
So far this is what I have:
public void countBinary(int n)
{
String s = "01";
countBinary(s, "", n);
}
private static void countBinary(String s, String chosen, int length)
{
if (s.length() == 0)
{
System.out.println(chosen);
}
else
{
char c = s.charAt(0);
s = s.substring(1);
chosen += c;
countBinary(s, chosen, length);
if (chosen.length() == length)
{
chosen = chosen.substring(0, chosen.length() - 1);
}
countBinary(s, chosen, length);
s = c + s;
}
}
When I run my code my output looks like this .
Can anyone explain to me why my method is not running the way I expect it to, and if possible show me a solution to my issue so that I might get the correct output? Thank you!
There are more efficient ways to do it, but this will give you a start:
public class BinaryPrinter {
static void printAllBinary(String s, int n) {
if (n == 0) System.out.println(s);
else {
printAllBinary(s + '0', n - 1);
printAllBinary(s + '1', n - 1);
}
}
public static void main(String [] args) {
printAllBinary("", 4);
}
}
I'll let you work out the more efficient way.
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