Fill array within nested loops

Question

I am trying to fill an array in two nested loops however for each second pPiece[] i want to give it a k attribute of 0 or 1 every second pPiece[] respectively

For example -

  pPieces[0] = new Piece(0,pcName,1);
  pPieces[1] = new Piece(1,pcName,1);
  pPieces[2] = new Piece(0,pcName,1);
  pPieces[3] = new Piece(1,pcName,1);
  etc....

What i have

private Piece pPieces[] = new Piece[8];

for(int j=0; j<pCount; j++) //pCount = 4
  {
      for(int k=0; k<pcCount; k++) //pcCount = 2
      {
          String pcName = "Piece " + (allocation());
          pPieces[j+k] = new Piece(k,pcName,1);
      }
  }

Doing it this way results in pPieces[] index being over written 4 times, i think. Is it possible to properly fill this array which should have 8 objects stored in it with every second 'k' equaling 0 or 1 respectively?

Tunaki · Accepted Answer · 2016-05-02 10:54:01Z

2

The issue in your current solution is that j+k will get the same value multiple times during the two loops:

for(int j=0; j<pCount; j++) //pCount = 4
{
    for(int k=0; k<pcCount; k++) //pcCount = 2
    {
        String pcName = "Piece " + (allocation());
        pPieces[j+k] = new Piece(k,pcName,1);
    }
}

For example, when j = 0 and k = 1, you will have j + k = 1. But you will also have that when j = 1 and k = 0.

The problem comes from the fact that you're incrementing the variable j by steps of 1 when you should increment it by steps of pcCount; and the related issue is that j should go to pCount*pcCount and not pCount only.

for(int j=0; j<pCount*pcCount; j+=pcCount) //<--- j+=pcCount here, not j++
{
    for(int k=0; k<pcCount; k++)
    {
        String pcName = "Piece " + allocation();
        pPieces[j+k] = new Piece(k,pcName,1);
    }
}

As a side-note, consider using more descriptive variable names instead of pCount and pcCount.

edited May 2, 2016 at 10:54

answered May 2, 2016 at 9:57

Tunaki

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2 Comments

danielb Over a year ago

i've done this and it's only filling my array with 2 Piece objects instead of 4. I made a loop to go through pPieces.length and print and only 2 spots were filled. I changed "(allocation());" to "(j+k));" btw

danielb Over a year ago

yes that got it to add 4 thank you. Both this answer and @Geeth Lochana's answers are correct. Thanks

Geeth Lochana · Accepted Answer · 2016-05-02 10:03:23Z

2

Refactor your code as follows, The issues is pPieces[j+k] = new Piece(k,pcName,1);

Your j+k => 0,1,1,2,2,3,3,4

Corrected Code

private Piece pPieces[] = new Piece[8];
int count=0;

for(int j=0; j<pCount; j++) //pCount = 4
  {
      for(int k=0; k<pcCount; k++) //pcCount = 2
      {
          String pcName = "Piece " + (allocation());
          pPieces[count++] = new Piece(k,pcName,1);
      }
  }

answered May 2, 2016 at 10:03

Geeth Lochana

18413 bronze badges

Comments

V.ERNST · Accepted Answer · 2016-05-02 10:01:31Z

0

Indeed, j+k will be overlapping. But 2j+k does not. You need to replace by :

private Piece pPieces[] = new Piece[8];

for(int j=0; j<pCount; j++) //pCount = 4
  {
      for(int k=0; k<pcCount; k++) //pcCount = 2
      {
          String pcName = "Piece " + (allocation());
          pPieces[2*j+k] = new Piece(k,pcName,1);
      }
  }
}

answered May 2, 2016 at 10:01

V.ERNST

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Comments

Jorn Vernee · Accepted Answer · 2016-05-02 10:03:40Z

0

The % operator can be of use here:

private Piece pPieces[] = new Piece[8];

for(int j = 0; j < pPieces.length; j++) {
    String pcName = "Piece " + (allocation());
    pPieces[j] = new Piece(j % 2,pcName,1);
}

The % (modulus) operator returns the remainder of integer division.

e.g.

0 % 2 = 0
1 % 2 = 1
2 % 2 = 0
3 % 2 = 1

Creating an alternation of 1 and 0.

answered May 2, 2016 at 10:03

Jorn Vernee

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4 Comments

danielb Over a year ago

this is designed to always fill my pPieces[] array. I don't want that to happen. But good idea!

Jorn Vernee Over a year ago

@danielb Wasn't that the goal? "Is it possible to properly fill this array which should have 8 objects stored in it..."

danielb Over a year ago

yes i would like it to be filled, but not unconditionally. Your idea is correct in the instance that I would always want it filled. Sorry, I dont think i explained it clearly enough

Jorn Vernee Over a year ago

@danielb Oh!, well this is just an example. You could put the for loop inside a method, and call that method when the condition applies.

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