Thread: How should I start creating this program? Help

A locker room has lockers numbered 0,1,2,...,1023 . All lockers are initially closed. The first person walks in and flips every locker The 2nd person flips every other locker (starting at 0) The 3rd person flips every third locker (starting at 0) . . . The 1024 person flips every 1024 locker (starting at 0) At the end, which lockers are open and which are closed?

What the program must do:
Write a program that creates an array of 1024 indices of type Boolean. Each index will represent a locker. You may assume that when the Boolean value is false, the locker is closed and when the value is true, the locker is open. This program will determine which lockers are open and closed at the end of the procedure above.
So it will output the locker number and whether or not it is open or closed.

For starters I was thinking to create an array called

boolean[] Lockers = new boolean[1024];

which will create 1024 indices with either true or false (open or closed) elements.
What I don't know is how to make every person go to their correct interval locker, and put it into a loop. When helping please don't use advanced code I have only learned arrays, while/dowhile/for loops, bubble sort*, user input.
I'm a complete newb at Java so any help would be appreciated.


*I also think bubble sort should be applied here, but I don't know how to apply it.
The following code is an unfinished bubble sorting program that I don't understand how to complete.

int []x = {4, 2, 3,5,1};
		int temp;
 
		for (int c=0; c<x.length-1; c++){
			if (x[c]>x[c+1]){
				temp = x[c+1];
				x[c+1]=x[c];
				x[c] = temp;
			}
		}

For the code above, the for-loop will move through the array x and swap any values if the current index is greater than the next index. To complete the bubble sort, the for loop above needs to be repeated until no swaps are made. Using the code above, add a Boolean variable called swap and a conditional loop that will repeat the for-loop until no more swaps are made.

'flipping' a locker would mean either to open or close it. Depending on the state that it's in, it will always do the opposite.
Also how would I make it so an individual door flipper flips the correct door?

I would recommend using the current value of your counter to also determine the increment.

Meaning, have a for loop that runs 1024 times. The number in the counter variable will tell us which person is running through (i.e. when it's 3, that means it's the fourth person going, since it starts counting at 0)
Inside that, have a for loop that simulates the person running through the locker room opening/closing lockers. The increment for this inside loop should be the current value of the counter of the outer loop.

Example of this situation:

int x, y;
 
for (x = 0;x < 1024;x++) { //Outer loop. Increments by 1
    for (y = 0;y < 1024;y += x + 1) { //Inner loop, increments by whatever the value of the outer loops is, +1
        //flip locker at the 'y' location
    }
}

--- Update ---

Originally Posted by illegit

'flipping' a locker would mean either to open or close it. Depending on the state that it's in, it will always do the opposite.
Also how would I make it so an individual door flipper flips the correct door?

Lockers[x] = !Lockers[x]

^ Not 100% on that but that's my first thought...I'm still learning too (;

How would I make the program output the locker number it is at, and whether or not it is open/closed.
output:
1 closed
2 open
3 closed
...

edit:

for(int c=0; c<Lockers.length; c++) {
	System.out.println(c +" " + Lockers[c]);
}

had to add the space between them to fix the error

Also, how can I make my boolean values output whether or not it is open/closed rather then true/false

--- Update ---

Originally Posted by rpressler

I would recommend using the current value of your counter to also determine the increment.

Meaning, have a for loop that runs 1024 times. The number in the counter variable will tell us which person is running through (i.e. when it's 3, that means it's the fourth person going, since it starts counting at 0)
Inside that, have a for loop that simulates the person running through the locker room opening/closing lockers. The increment for this inside loop should be the current value of the counter of the outer loop.

So like this:

boolean[] Lockers = new boolean[1024];
	for(int c=0; c<Lockers.length; c++) {
		for(int y=0; y<Lockers.length; y+=c+1) {
			Lockers[y]=!Lockers[y]; 
		System.out.println(Lockers[y]);
			}
		}

?

When you need to make a program do something, try to break it down into steps you can do one step at a time.

What you want to do is print if a locker is open or closed. So pseudo code may look like this:

print "locker number " + lockerNumber + " is"
if : the locker value is true (this means open)
  println " open."
else
 println " closed."

...and you want to do that "for each" locker, so set up a loop to go through each one

In the end you should see one of the following for each locker number:
Locker number 0 is Open.
Locker number 0 is Closed.
...but with the correct locker number depending on which number the loop is on