tasks a-s

Task/Power-set/PHP/power-set-1.php

@@ -0,0 +1,59 @@
+<?php
+function get_subset($binary, $arr) {
+  // based on true/false values in $binary array, include/exclude
+  // values from $arr
+  $subset = array();
+  foreach (range(0, count($arr)-1) as $i) {
+    if ($binary[$i]) {
+      $subset[] = $arr[count($arr) - $i - 1];
+    }
+  }
+  return $subset;
+}
+
+function print_array($arr) {
+  if (count($arr) > 0) {
+    echo join(" ", $arr);
+  } else {
+    echo "(empty)";
+  }
+  echo '<br>';
+}
+
+function print_power_sets($arr) {
+  echo "POWER SET of [" . join(", ", $arr) . "]<br>";
+  foreach (power_set($arr) as $subset) {
+    print_array($subset);
+  }
+}
+
+function power_set($arr) {
+  $binary = array();
+  foreach (range(1, count($arr)) as $i) {
+    $binary[] = false;
+  }
+  $n = count($arr);
+  $powerset = array();
+
+  while (count($binary) <= count($arr)) {
+    $powerset[] = get_subset($binary, $arr);
+    $i = 0;
+    while (true) {
+      if ($binary[$i]) {
+        $binary[$i] = false;
+        $i += 1;
+      } else {
+        $binary[$i] = true;
+        break;
+      }
+    }
+    $binary[$i] = true;
+  }
+
+  return $powerset;
+}
+
+print_power_sets(array());
+print_power_sets(array('singleton'));
+print_power_sets(array('dog', 'c', 'b', 'a'));
+?>

Task/Power-set/PHP/power-set-2.php

@@ -0,0 +1,21 @@
+POWER SET of []
+POWER SET of [singleton]
+(empty)
+singleton
+POWER SET of [dog, c, b, a]
+(empty)
+a
+b
+a b
+c
+a c
+b c
+a b c
+dog
+a dog
+b dog
+a b dog
+c dog
+a c dog
+b c dog
+a b c dog