Problem from the book

[Mike_Shn]

Hello
Does someone know an intelegent solution for the following problem:
Imagine you need to open a standard combination dial lock but don't know the combination and don't have a pair of bolt cutters. Write a program that prints all possible combinations so you can print them on a piece of paper and check off each one as you try it. Assume the numbers on the dial range from zero to thirty-six and three numbers in sequence are needed to open the lock.
Thanks a lot

[Nathan Pruett]

That's pretty easy....

public class CrackIt
{
    public static void main( String args[] )
    {
        for( int i = 0; i < 37; i++ )
        {
            for( int j = 0; j < 37; j++ )
            {
                for( int k = 0; k < 37; k++ )
                {
                    System.out.println( Integer.toString( i ) +
                                        "-" + 
                                        Integer.toString( j ) +
                                        "-" +
                                        Integer.toString( k ) );
                }
            }
        }
    }
}

Are you sure this isn't some kind of class assignment or something?

-Nate
[This message has been edited by Nathan Pruett (edited September 11, 2001).]

[Michael Fitzmaurice]

Hi Mike
You can do this type of operation using nested for loops. The following code gives you the logic, all you need to do is change the value of the <code>MAXIMUM_VALUE</code> constant from 1 to 36.
I have used a StringBuffer rather than printing directly to the screen during the loop iterations, but if you wanted to do it that way, just replace the call to <code>Sbuf.append()</code> with a <code>System.out.println()</code> (bear in mind this will probably slow the program down even more).
It's also probably worth mentioning that when you run this code for numbers ranging from 0 to 36 rather than 0 to 1 it will dump 50653 (37 * 37 * 37) lines of output to your console, most of which you will obviously not be able to see when the program concludes. If you really want to print them to a piece of paper, I would suggest writing them out to a file instead of/as well as writing them to the screen. However, I suspect the question was just an exercise in using nested loops, so that's all I've done here.
<code><pre>
public class CombinationLock
{
// using a constant for the maximum number allowed means
// that we can change it more easily than if it was
// hardcoded into the loops themselves
private static final int MAXIMUM_VALUE= 1;

public static void main(String[] args)
{
StringBuffer sBuf = new StringBuffer();
int possibleCombinations = 0;
int firstNumber, secondNumber, thirdNumber;
for(int i = 0; i <= MAXIMUM_VALUE; i++)
{
firstNumber = i;
for(int j = 0; j <= MAXIMUM_VALUE; j++)
{
secondNumber = j;
for(int k = 0; k <= MAXIMUM_VALUE; k++)
{
thirdNumber = k;
possibleCombinations++;
sBuf.append("\n"
+ firstNumber + " "
+ secondNumber + " "
+ thirdNumber);
}// end of third loop
}// end of second loop
}// end of 1st loop
System.out.println( "POSSIBLE COMBINATIONS FOR 0 TO " + MAXIMUM_VALUE +
"\n" + sBuf.toString() );
// :NB: total possible combinations should equal size of range raised
// to the power of the number of locks (i.e. 3 in this case)
System.out.println("TOTAL OF " + possibleCombinations + " POSSIBLE COMBINATIONS");
}//end of main
}//end of class
</code></pre>
[This message has been edited by Michael Fitzmaurice (edited September 11, 2001).]
[This message has been edited by Michael Fitzmaurice (edited September 11, 2001).]