Array selection by binary array

Question

We have an array of random lenght and random numbers eg.

[12, 2345, 232, 52, 24].

And we Want to select only those defined by a binary number so eg.

5= 101 = [0, 0, 1, 0, 1]

so the Array X which i want to get is

[0, 0, 232, 0, 24];

Example

int[] x = {12, 2345, 232, 52, 24};
int b = 5;
int[] X = eliminate(x, b);

//
x = [12, 2345, 232, 52, 24]
b = [ 0,    0,   1,  0,  1]
X = [ 0,    0, 232,  0, 24]

any quick way to do this?

Thanks

@Mazmart I was unsure if you needed a int -> bitarray conversion as well, so I included one in my answer. — Angelo Fuchs, Sep 30 '13 at 09:16
sorry. It was a typo. i've made up the numbers on the go as i didn't have any real test numbers then. — Mazmart, Oct 02 '13 at 08:26

score 3 · Accepted Answer · edited May 23 '17 at 10:32

Using a BitSet might help, for conversions between int and BitSet have a look here: BitSet to and from integer/long

Here's a quick hack using the Bits class from the link:

public static int[] eliminate( int[] x, int b) {
  BitSet bs = Bits.convert( b );
  int[] X = new int[x.length];

  for( int i = 0; i < x.length; i++){
    if( bs.get( x.length - (i + 1) ) ){
      X[i] = x[i];
    }
    else {
      X[i] = 0;
    }
  }

  return X;
}

Result would be:

x = [12, 2345, 232, 52, 24]
b = 5 (i.e. 101 binary)
X = [0, 0, 232, 0, 24]

Note that if you want to define bits directly, you can just set them in the BitSet.

score 1 · Answer 2 · answered Sep 30 '13 at 08:32

1

Just a for-loop

int[] newarray = new int[length];
for(int i = 0; i < length; i++)
{
    if(b[i]==1)
       newarray[i] = x[i];
    else
       newarray[i] = 0;
}

Just make sure the length everywhere is consistent.

answered Sep 30 '13 at 08:32

Loki

4,065
4
29
51

score 0 · Answer 3 · answered Sep 30 '13 at 08:36

0

As this:

int i = 3;
int[] yourArray;
for (int i = 0; i < yourArray.length; i++) {
    yourArray[i] = yourArray[i] & i == i ? yourArray[i] : 0;
}

answered Sep 30 '13 at 08:36

Alex Suo

2,977
1
14
22

Angelo Fuchs · Answer 4 · 2013-09-30T09:26:26.787

Try this:

    String binSt = Integer.toBinaryString(5); // has no leading 0s
    byte[] x = {12, 21, 21, 52, 24};
    byte[] xResult = new byte[x.length];
    int offset = x.length - binSt.length(); // to simulate leading 0s
    for (int i = 0; i < xResult.length; i++) {
        xResult[i] = (i-offset < binSt.length() && i-offset >= 0 && binSt.charAt(i-offset) == '1' ? x[i] : 0);
    }
    System.out.println(Arrays.toString(xResult));

Array selection by binary array

4 Answers4