Exponent loop and recursive example

Power.php

@@ -0,0 +1,70 @@
+<?php
+/**
+ * Exponent Problems
+ *
+ * Raise number to a power without built-in functions
+ *
+ * NOTE: One of the problem constraints (because of time) was to only support positive integers
+ *
+ * @category InterviewQuestions
+ * @package Power
+ * @author Michael Reeves <mike.reeves@gmail.com>
+ * @date 2013-05-10
+ *
+ */
+
+// loop example
+function powLoop($base, $exp) {
+    // TODO: add validation for input vars
+	if ($exp < 1 || !is_integer($exp)) {
+		die('Exponent does not meet problem constraints.');
+	} elseif ($exp === 1){
+        return $base;
+    } else { // assume only positive exponents
+        $answer = 1;
+        for ($i = 0; $i < $exp; $i++){
+            $answer = $answer * $base;
+        } 
+        return $answer;
+    }
+}
+
+// loop test
+echo '<h2>Loop example</h2>';
+echo powLoop(10, 1). ' should be 10.<br/>'; // 10
+echo powLoop(10, 2). ' should be 100.<br/>'; // 100
+echo powLoop(2, 3). ' should be 8.<br/>'; // 8
+echo powLoop(1500, 1). ' should be 1500.<br/>'; // 1500
+
+
+// recursion example
+function powWrapper($base, $exp) {
+    return powRecursive(1, $base, $exp);
+}
+
+function powRecursive($total, $base, $exp) {
+    $newTotal = $total * $base;
+    if ($exp < 1 || !is_integer($exp)) {
+        die('Exponent does not meet problem constraints.');
+    } elseif ($exp === 1) {
+        return($newTotal);
+    } else {
+        $newExp = $exp - 1;
+        return powRecursive($newTotal, $base, $newExp);
+    }
+}
+
+// recursion test
+echo '<h2>Recursion example</h2>';
+echo powWrapper(10, 1). ' should be 10.<br/>'; // 1000
+echo powWrapper(10, 3). ' should be 1000.<br/>'; // 1000
+echo powWrapper(2, 3). ' should be 8.<br/>'; // 8
+echo powWrapper(1500, 1). ' should be 1500.<br/>'; // 1500
+
+/*
+unraveling recursion manually for 10, 3 example:
+1, 10, 3
+10, 10, 2
+100, 10, 1
+return 1000
+*/