User specified 2d array element values

Question

        for (int i = 0; i < height; i++) {
            for (int j = 0; j < width; j++) {
                while (treasures >= 0) {
                    mapArray[i][j] = rnd.nextInt(2);
                    treasures -= 1;
                }
            }
        }

The user specifies the array's height and width, along with how many "treasures" this array contains. The code should cycle through all of the array's elements, giving them a value of either 0 or 1 ( until the number of treasures entered by the user reaches 0 ).

Treasure indication is 1.

Right now the for loops only target the first ( [0] [0] ) element.

Answer 1

You should eliminate the while loop, since it prevents i and j from being incremented until it ends, which is why only mapArray[0][0] is assigned.

    for (int i = 0; i < height && treasures >= 0; i++) {
        for (int j = 0; j < width && treasures >= 0; j++) {
            mapArray[i][j] = rnd.nextInt(2);
            treasures -= 1;            
        }
    }

Note that if treasures < height * width , some elements of the array will contain 0 by default.

Answer 2

Remove the while loop, as it forces to only run for mapArray[0][0] and while loop ends when treasures become zero. This eventually terminates all the loops.

Answer 3

I think number of "treasures" is associated with "1". So if the user wants the array's height to be 4 and width also 4 and "treasures" to be for example 3 i would expect something like this: three "1" and rest "0"

     0110
     1000
     0000
     0000

in that case you may try

Random rnd = new Random();
    int [][] grid = new int[height][width];
    int treasures = 3;

        for (int[] row : grid){                
            for (int n : row){                    
                if(treasures>0){
                    n = rnd.nextInt(2);
                    if(n==1){
                       treasures -= 1;
                    }
                }
                System.out.print(n);
            }
          System.out.println();
        }

Answer 4

To understand your code, I encourage you to take a pen and write what your code do.

For example :

• Input height=2, width=3, treasures=1
• Step 1 i=0 and height>i => 2>1 => continue (height=2, width=3, treasures=1, i=0)
• Step 2 j=0 and width>j => 3>0 => continue (height=2, width=3, treasures=1, i=0, j=0)
• Step 3 treasure >= 0 => 1>=0 => continue
• Step 4 mapArray[i][j] = rnd.nextInt(2); => mapArray[0][0] = rnd.nextInt(2);
• Step 5 treasures -= 1 => treasure = 0 (height=2, width=3, treasures=0, i=0, j=0)
• Step 6 treasure >= 0 => 0>=0 => continue [I think you don't want this but it's not the problem that causes your question]
• Step 7 mapArray[i][j] = rnd.nextInt(2); => mapArray[0][0] = rnd.nextInt(2); ...

Now a few hints to continue :

The code should cycle through all of the array's elements, giving them a value of either 0 or 1 ( until the number of treasures entered by the user reaches 0 ).

You can translate it into : I need to place my X treasures into my map.

So the while loop is a good idea, but it's actually in a wrong place. Delete the 2 for loops and keep only the while loop to begin with.

Now think and find a way to put these treasures, one by one, in the right place on your map.

Later, if you need to run through you map, then you will need your 2 for loops. It can be usefull to display your map for example.

Don't forget to check that your inputs are valid.