Truth Table / Power Set

Output:
0 0 0 
0 0 1 
0 1 0 
0 1 1 
1 0 0 
1 0 1 
1 1 0 
1 1 1 

printTruthTable("", 0, 3);

$originalArr = array('a', 'b', 'c');
$outputArr = array();
powerSet("", 0, 3);
var_dump($outputArr);

function printTruthTable($str, $start, $strLength) {
  if ($start === $strLength) {
    if (/*Truth Table*/) {
      var_dump($str);
    }
    if (/*Power Set*/) {
      global $originalArr;
      global $outputArr;
      
      $tempArr = array();
      for($i=0; $i<$strLength; $i++){
        if ($str[$i] === 1) {
          array_push($tempArr, $originalArr[$i]);
        }
      }
      array_push($outputArr, $tempArr);
    }
    
    return;
  }
  $str[$start] = 0;
  printTruthTable($str, $start+1, $strLength);
  
  $str[$start] = 1;
  printTruthTable($str, $start+1, $strLength);
}

OR

function printPowerSet($set, $set_size)
{
    /*set_size of power set of a set with set_size
      n is (2**n -1)*/
    $pow_set_size = pow(2, $set_size);
 
    for($counter = 0; $counter < $pow_set_size; $counter++)
    {
      for($j = 0; $j < $set_size; $j++)
       {
          if($counter & (1 << $j))
            echo $set[$j]; // echo 
       }
       echo PHP_EOL;
    }
}
 
$set = 'abc';
printPowerSet($set, 3);

Print all permutations of a string

permute("123", 0, 3);

function permute($str, $start, $strLength) {
  if ($start === $strLength) {
    var_dump($str);
    return;
  }
  for ($i=$start; $i<$strLength; $i++) {
    swap($str, $i, $start);
    permute($str, $start+1, $strLength);
    swap($str, $start, $i);
  }
}
 
function swap(&$str, $pos1, $pos2) { 
  $tmp = $str[$pos1]; 
  $str[$pos1] = $str[$pos2]; 
  $str[$pos2] = $tmp; 
}

Print all possible combinations of strings that can be made using a keypad given a number

telKeys("2133004655", "2133004655", 0, 10);

$keypad = array("ABC", "DEF", "GHI", "JKL", "MNO", "PQR", "STU", "VWX", "YZ");
function telKeys($original, $new, $start, $strLength) {
  global $keypad;
  if ($start === $strLength) {
    var_dump($new);
    return;
  }

    $new[$start] = $keypad[$original[$start]][0];
    telKeys($original, $new, $start+1, $strLength);
    
    $new[$start] = $keypad[($original[$start])][1];
    telKeys($original, $new, $start+1, $strLength);
    
    if(($original[$start]) < 8) {
        $new[$start] = $keypad[($original[$start])][2];
        telKeys($original, $new, $start+1, $strLength);
    }
}

Print given string in all combinations of uppercase and lowercasecharacters

Given a string we need to print the string with all possible combinations of the uppercase and lowercase characters in the string.

So given a string "abc", we need to print the following:
ABC
ABc
AbC
Abc
aBC
aBc
abC
abc

Solution is a simple recursive approach where we call the function again and again once with a character in lower case and another time with the same character in upper case. The code is similar to what we would write for all permutations of a string.

lowerUpper("abc", 0, 3);

function lowerUpper($str, $start, $strLength) {
  if ($start === $strLength) {
    var_dump($str);
    return;
  }
    
  $str[$start] = strtoupper($str[$start]);
  lowerUpper($str, $start+1, $strLength);
    
  $str[$start] = strtolower($str[$start]);
  lowerUpper($str, $start+1, $strLength);
}