clean up day 2 a bit

Author: dannyvankooten

2024-php/01.php

@@ -33,8 +33,8 @@
 	$pt2 += $a[$i] * $occurs;
 }
 
-echo "Day 1: Historian Hysteria", PHP_EOL;
+echo "--- Day 1: Historian Hysteria ---", PHP_EOL;
 echo "Part 1: ", $pt1, PHP_EOL;
-echo "Part 1: ", $pt2, PHP_EOL;
+echo "Part 2: ", $pt2, PHP_EOL;
 echo "Took ", microtime(true) - $time_start, " seconds", PHP_EOL;
 echo PHP_EOL;

2024-php/02.php

@@ -1,9 +1,9 @@
 <?php
 $time_start = microtime(true);
 
-function is_safe($numbers): bool
+function is_safe(array $numbers): bool
 {
-	$diffs = [];
+	$diff_prev = 0;
 	for ($i = 1; $i < count($numbers); $i++) {
 		$diff = $numbers[$i] - $numbers[$i - 1];
 
@@ -12,18 +12,12 @@ function is_safe($numbers): bool
 			return false;
 		}
 
-		$diffs[] = $diff;
-	}
-
-	// sign of each diff must be the same as all other elements
-	for ($i = 1; $i < count($diffs); $i++) {
-		if ($diffs[$i] > 0 && $diffs[$i-1] < 0) {
+		// sign of each diff must match preceding diff
+		if ($i >= 2 && $diff > 0 != $diff_prev > 0) {
 			return false;
 		}
 
-		if ($diffs[$i] < 0 && $diffs[$i-1] > 0) {
-			return false;
-		}
+		$diff_prev = $diff;
 	}
 
 	return true;
@@ -38,15 +32,17 @@ function is_safe($numbers): bool
 	if (is_safe($numbers)) {
 		$pt1++;
 		$pt2++;
-	} else {
-		for ($i = 0; $i < count($numbers); $i++) {
-			$copy = $numbers;
-			unset($copy[$i]);
-			$copy = array_values($copy);
-			if (is_safe($copy)) {
-				$pt2++;
-				break;
-			}
+		continue;
+	}
+
+	// for part 2, brute-force remove each number and see if safe
+	for ($i = 0; $i < count($numbers); $i++) {
+		$copy = $numbers;
+		unset($copy[$i]);
+		$copy = array_values($copy);
+		if (is_safe($copy)) {
+			$pt2++;
+			break;
 		}
 	}
 }