Can you find an efficient solution to this bit manipulation problem?

Replies

• 

  PraveenKumar Purushothaman

  What is the language you are trying to implement? Coz, in PHP it is very easy! 😀
• 

  eternalthinker

  @Praveen
  Bit operations shouldn't be very different throughout languages, I suppose.
  Or does PHP have any special operators which makes the solution easier?
  
  In any case, do share your solution 😀
• 

  PraveenKumar Purushothaman

  eternalthinker

  @Praveen
  Bit operations shouldn't be very different throughout languages, I suppose.
  Or does PHP have any special operators which makes the solution easier?
  
  In any case, do share your solution 😀

  PHP has associative array technique, which makes declaration of 2D Arrays / Maps easier... 😀
• 

  PraveenKumar Purushothaman

  For eg., consider this program:

  php
    $n = 5;
    $a = array();
    for($i = 0; $i < $n; $i++)
        for($j = 0; $j < $n; $j++)
            $a[$i][$j] = decbin($i + $j);
    var_dump($a);
?>

  The output is

  array(5) {
    [0]=>
    array(5) {
      [0]=>
      string(1) "0"
      [1]=>
      string(1) "1"
      [2]=>
      string(2) "10"
      [3]=>
      string(2) "11"
      [4]=>
      string(3) "100"
    }
    [1]=>
    array(5) {
      [0]=>
      string(1) "1"
      [1]=>
      string(2) "10"
      [2]=>
      string(2) "11"
      [3]=>
      string(3) "100"
      [4]=>
      string(3) "101"
    }
    [2]=>
    array(5) {
      [0]=>
      string(2) "10"
      [1]=>
      string(2) "11"
      [2]=>
      string(3) "100"
      [3]=>
      string(3) "101"
      [4]=>
      string(3) "110"
    }
    [3]=>
    array(5) {
      [0]=>
      string(2) "11"
      [1]=>
      string(3) "100"
      [2]=>
      string(3) "101"
      [3]=>
      string(3) "110"
      [4]=>
      string(3) "111"
    }
    [4]=>
    array(5) {
      [0]=>
      string(3) "100"
      [1]=>
      string(3) "101"
      [2]=>
      string(3) "110"
      [3]=>
      string(3) "111"
      [4]=>
      string(4) "1000"
    }
  }

  And, for this code:

  php
    $n = 5;
    $a = array();
    for($i = 0; $i < $n; $i++)
        for($j = 0; $j < $n; $j++)
            $a[$i][$j] = decbin($i + $j);
    for($i = 0; $i < $n; $i++)
    {
        for($j = 0; $j < $n; $j++)
            echo $a[$i][$j] . "\t";
        echo "\n";
    }
?>

  The output is

  0       1       10      11      100
  1       10      11      100     101
  10      11      100     101     110
  11      100     101     110     111
  100     101     110     111     1000

  Did I understand your problem rightly?
• 

  PraveenKumar Purushothaman

  @ET: Finally you can arrive the same solution of yours in this way:

  php
    $n = 5;
    $a = array();
    for($i = 0; $i < $n; $i++)
        for($j = 0; $j < $n; $j++)
            $a[$i][$j] = decbin($i + $j);
    for($i = 0; $i < $n; $i++)
        for($j = 0; $j < $n; $j++)
            echo "Map ($i, $j) is {$a[$i][$j]}\n";
?>

  And the output for the same is:

  Map (0, 0) is 0
  Map (0, 1) is 1
  Map (0, 2) is 10
  Map (0, 3) is 11
  Map (0, 4) is 100
  Map (1, 0) is 1
  Map (1, 1) is 10
  Map (1, 2) is 11
  Map (1, 3) is 100
  Map (1, 4) is 101
  Map (2, 0) is 10
  Map (2, 1) is 11
  Map (2, 2) is 100
  Map (2, 3) is 101
  Map (2, 4) is 110
  Map (3, 0) is 11
  Map (3, 1) is 100
  Map (3, 2) is 101
  Map (3, 3) is 110
  Map (3, 4) is 111
  Map (4, 0) is 100
  Map (4, 1) is 101
  Map (4, 2) is 110
  Map (4, 3) is 111
  Map (4, 4) is 1000

  This one is identical to what you asked! 😀
• 

  eternalthinker

  @Praveen
  I like the idea of storing all the patterns in an array once, and only referring to it subsequently.
  
  Anyhow, did you check the bit patterns in the question? There is a particular logic in how they are arranged.
  I think I should've been more clear in the question!
  
  Please see the updated question 😀
• 

  PraveenKumar Purushothaman

  eternalthinker

  @Praveen
  I like the idea of storing all the patterns in an array once, and only referring to it subsequently.
  
  Anyhow, did you check the bit patterns in the question? There is a particular logic in how they are arranged.
  I think I should've been more clear in the question!
  
  Please see the updated question 😀

  I couldn't see the update buddy. Say once more na?
• 

  eternalthinker

  @Praveen
  
  I was updating it now! Check it again.
• 

  PraveenKumar Purushothaman

  eternalthinker

  @Praveen
  
  I was updating it now! Check it again.

  Okay, got it... Gimme some time... Will do something.. 😁