Booj Code Test - Tom Krepp

EquilibriumIndex.php

@@ -1,9 +1,49 @@
 <?php
 
-# Put a valid docblock here!
+/**
+ * This function, given a sequence, returns its equilibrium indices (if any).
+ *
+ * I first thought about using the built in array_sum and array_slice functions, but they are slow on very large/long sequences.  Instead I decided on solving it with a few nested for loops.
+ *
+ * My first step was to figure out how to loop through the array, and seperate the numbers lower than the current index being tested into one set - and the numbers higher than the current index into another.  The "echo's" I left in the code helped me to verify that I was indeed looping through the array correctly, and hitting the correct indices each time through the loop.  I didn't check for all edge cases, but in the future I would add error handling to check if all elements in the given array are indeed integers.
+ *
+ * @param array $arr
+ * @return array
+ * @throws Exception If element in array is not an integer
+ */
 function getEquilibriums($arr) {
-	$output = array();
-	# Logic goes here!
-	return $output;
+  $output = array();
+
+  # the sum of both the low & high number groups are set to 0, at the start of the outer loop
+  for($i = 0; $i < count($arr); $i++) {
+    $low = 0;
+    $high = 0;
+    echo "\n\n** Loop #$i **\n";
+
+    # Starting at the zero index of the array, this loop adds the sum of elements at lower indices
+    for($x = 0; $x < $i; $x++) {
+      $low += $arr[$x];
+      echo "low: $x\n";
+    }
+
+    # Starting at the last index of the array, this loop adds the sum of elements at higher indices
+    for($y = count($arr) - 1; $y > $i; $y--) {
+      $high += $arr[$y];
+      echo "high: $y\n";
+    }
+
+    # Checks if the sum of the high numbers is equal to the sum of the low numbers. If the sums are equal - the current index is confirmed as an equilibrium index.
+    if($high === $low) {
+      array_push($output,$i);
+    }
+  }
+
+  # Prints message if no equilibrium indices are found
+  if(count($output) == 0) {
+    echo "\nNo equilibrium indices found";
+    return;
+  }
+  return $output;
 }
-
+
+?>