day 2

public/days/Day2.php

@@ -0,0 +1,91 @@
+<?php
+
+final class Day2 extends Day {
+
+	function part1(): string {
+		$safeCount = 0;
+
+		foreach ($this->input as $line){
+			$levels = array_map('intval', explode(' ', $line));
+
+			$isSafe = true;
+
+
+			$direction = null;
+			for ($i = 0; $i < count($levels) - 1; $i++){
+				$levelNow = $levels[$i];
+				$levelThen = $levels[$i + 1];
+
+				$change = abs($levelThen - $levelNow);
+				if ($change < 1 || $change > 3){
+					$isSafe = false;
+					break;
+				}
+
+				if ($direction === null){
+					$direction = $levelThen > $levelNow;
+				}
+
+				if ($direction !== ($levelThen > $levelNow)){
+					$isSafe = false;
+					break;
+				}
+			}
+
+			if ($isSafe)
+				$safeCount++;
+		}
+
+		return strval($safeCount);
+	}
+
+	function part2(): string {
+		$safeCount = 0;
+
+		foreach ($this->input as $line){
+			$levels = array_map('intval', explode(' ', $line));
+
+			$isSafe = false;
+
+			for ($removeLevelIndex = -1; $removeLevelIndex < count($levels); $removeLevelIndex++){
+				$localLevels = $levels;
+				if ($removeLevelIndex > -1){
+					array_splice($localLevels, $removeLevelIndex, 1);
+				}
+
+				$levelSetIsSafe = true;
+				$direction = null;
+				for ($i = 0; $i < count($localLevels) - 1; $i++){
+					$levelNow = $localLevels[$i];
+					$levelThen = $localLevels[$i + 1];
+
+					$change = abs($levelThen - $levelNow);
+					if ($change < 1 || $change > 3){
+						$levelSetIsSafe = false;
+						break;
+					}
+
+					if ($direction === null){
+						$direction = $levelThen > $levelNow;
+					}
+
+					if ($direction !== ($levelThen > $levelNow)){
+						$levelSetIsSafe = false;
+						break;
+					}
+				}
+				if ($levelSetIsSafe){
+					$isSafe = true;
+					break;
+				}
+			}
+
+			if ($isSafe)
+				$safeCount++;
+
+
+		}
+
+		return strval($safeCount);
+	}
+}