Day 2 solution.

2015/days/day1.php

@@ -8,15 +8,12 @@
  * Runtime: ~0.158ms
  */
 function day1solution1() {
-  $start_time = microtime(true);
   $instructions = file_get_contents('./2015/inputs/day1.txt');
   $up_floors = substr_count($instructions, "(");
   $down_floors = substr_count($instructions, ")");
   $total = $up_floors - $down_floors;
-  echo "The answer is $total\n";
-  $end_time = microtime(true);
-  $execution_time = ($end_time - $start_time);
-  echo $execution_time * 1000 . "\n";
+
+  return $total;
 }
 
 /*
@@ -25,7 +22,6 @@ function day1solution1() {
  * Runtime: ~.33ms
  */
 function day1solution1b() {
-  $start_time = microtime(true);
   $instructions = file_get_contents('./2015/inputs/day1.txt');
   $chars = str_split($instructions);
   $position = 1;
@@ -42,8 +38,6 @@ function day1solution1b() {
       $position++;
     }
   };
-  echo "The position is $position\n";
-  $end_time = microtime(true);
-  $execution_time = ($end_time - $start_time);
-  echo $execution_time * 1000 . "\n";
+
+  return $position;
 }

2015/days/day2.php

@@ -0,0 +1,98 @@
+<?php
+
+class Box {
+
+  protected $length;
+  protected $width;
+  protected $height;
+
+  /**
+   * @param mixed $property
+   */
+  public function get($property): int|string {
+    return $this->{$property};
+  }
+
+  /**
+   * @param mixed $property
+   * @param mixed $value
+   */
+  public function set($property, $value): void {
+    $this->{$property} = $value;
+  }
+
+  /**
+   * Calculates the required sq footage of paper needed.
+   */ 
+  public function calculateRequiredFootage(): int {
+    $side_1 = $this->length * $this->width;
+    $side_2 = $this->width * $this->height;
+    $side_3 = $this->height * $this->length;
+    $extra = min($side_1, $side_2, $side_3);
+    $area = 
+      (2 * $side_1) +
+      (2 * $side_2) +
+      (2 * $side_3);
+
+    return $area + $extra;
+  }
+
+  public function calculateShortestPerimeter() {
+    $perimeter_1 = 2 * $this->length + 2 * $this->width;
+    $perimeter_2 = 2 * $this->width + 2 * $this->height;
+    $perimeter_3 = 2 * $this->height + 2 * $this->length;
+
+    return min($perimeter_1, $perimeter_2, $perimeter_3);
+  }
+
+  /*
+   * Extracts the dimensions from a string.
+   */
+  public function extractDimensions(string $dimensions): void {
+    $dimensions_exploded = explode("x", $dimensions);
+    $this->length = $dimensions_exploded[0];
+    $this->width = $dimensions_exploded[1];
+    $this->height = $dimensions_exploded[2];
+  }
+
+  public function calculateRibbonRequirements() {
+    $bow = $this->length * $this->width * $this->height;
+    $shortest_perimeter = $this->calculateShortestPerimeter();
+
+    return $bow + $shortest_perimeter;
+  }
+
+}
+
+function day2part1() {
+  $box_dimension_list = file_get_contents('./2015/inputs/day2.txt');
+  $box_dimension_list = explode(PHP_EOL, $box_dimension_list);
+  $wrapping_paper_total = 0;
+  foreach ($box_dimension_list as $box_dimensions) {
+    if (strlen($box_dimensions) < 1) {
+      continue;
+    }
+    $box = new Box();
+    $box->extractDimensions($box_dimensions);
+    $wrapping_paper_total = $wrapping_paper_total + $box->calculateRequiredFootage();
+  }
+  return $wrapping_paper_total;
+}
+
+function day2part1b() {
+  $box_dimension_list = file_get_contents('./2015/inputs/day2.txt');
+  $box_dimension_list = explode(PHP_EOL, $box_dimension_list);
+  $ribbon_requirements = 0;
+  foreach ($box_dimension_list as $box_dimensions) {
+    if (strlen($box_dimensions) < 1) {
+      continue;
+    }
+    $box = new Box();
+    $box->extractDimensions($box_dimensions);
+    $ribbon_requirements = $ribbon_requirements + $box->calculateRibbonRequirements();
+  }
+
+  return $ribbon_requirements;
+}
+
+

2015/solutions.php

@@ -5,6 +5,15 @@ foreach ($days as $day) {
   require($day);
 }
 
-$d1 = day1solution1();
-$d1b = day1solution1b();
+$solutions = [];
+$solutions['day_1']['part_1'] = day1solution1();
+$solutions['day_1']['part_2'] = day1solution1b();
+$solutions['day_2']['part_1'] = day2part1();
+$solutions['day_2']['part_2'] = day2part1b();
 
+// OUTPUT THE SOLUTIONS WE HAVE.
+foreach ($solutions as $day => $parts) {
+  foreach ($parts as $part => $answer) {
+    echo "*** The answer to $day $part is: $answer ***\n";
+  }
+}