2024 Day 01 part 1

Author: sprak3000

2024/day-02.php

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+<?php
+
+require __DIR__ . '/../vendor/autoload.php';
+
+use adventofcode\Year2024\ReactorReportParser;
+
+/**
+ * --- Day 2: Red-Nosed Reports ---
+ *
+ * Fortunately, the first location The Historians want to search isn't a long walk from the Chief Historian's office.
+ *
+ * While the Red-Nosed Reindeer nuclear fusion/fission plant appears to contain no sign of the Chief Historian, the
+ * engineers there run up to you as soon as they see you. Apparently, they still talk about the time Rudolph was saved
+ * through molecular synthesis from a single electron.
+ *
+ * They're quick to add that - since you're already here - they'd really appreciate your help analyzing some unusual
+ * data from the Red-Nosed reactor. You turn to check if The Historians are waiting for you, but they seem to have
+ * already divided into groups that are currently searching every corner of the facility. You offer to help with the
+ * unusual data.
+ *
+ * The unusual data (your puzzle input) consists of many reports, one report per line. Each report is a list of numbers
+ * called levels that are separated by spaces. For example:
+ *
+ * 7 6 4 2 1
+ * 1 2 7 8 9
+ * 9 7 6 2 1
+ * 1 3 2 4 5
+ * 8 6 4 4 1
+ * 1 3 6 7 9
+ *
+ * This example data contains six reports each containing five levels.
+ *
+ * The engineers are trying to figure out which reports are safe. The Red-Nosed reactor safety systems can only tolerate
+ * levels that are either gradually increasing or gradually decreasing. So, a report only counts as safe if both of the
+ * following are true:
+ *
+ *   - The levels are either all increasing or all decreasing.
+ *   - Any two adjacent levels differ by at least one and at most three.
+ *
+ * In the example above, the reports can be found safe or unsafe by checking those rules:
+ *
+ *   - 7 6 4 2 1: Safe because the levels are all decreasing by 1 or 2.
+ *   - 1 2 7 8 9: Unsafe because 2 7 is an increase of 5.
+ *   - 9 7 6 2 1: Unsafe because 6 2 is a decrease of 4.
+ *   - 1 3 2 4 5: Unsafe because 1 3 is increasing but 3 2 is decreasing.
+ *   - 8 6 4 4 1: Unsafe because 4 4 is neither an increase or a decrease.
+ *   - 1 3 6 7 9: Safe because the levels are all increasing by 1, 2, or 3.
+ *
+ * So, in this example, 2 reports are safe.
+ *
+ * Analyze the unusual data from the engineers. How many reports are safe?
+ */
+
+$reactorReportParser = new ReactorReportParser();
+
+$reports = file(__DIR__ . '/inputs/day-02.input', FILE_IGNORE_NEW_LINES);
+
+$count = $reactorReportParser->findSafeReportsCount($reports);
+print('There are ' . $count . " safe reports.\n");
+
+/**
+ * --- Part Two ---
+ *
+ * The engineers are surprised by the low number of safe reports until they realize they forgot to tell you about
+ * the Problem Dampener.
+ *
+ * The Problem Dampener is a reactor-mounted module that lets the reactor safety systems tolerate a single bad level
+ * in what would otherwise be a safe report. It's like the bad level never happened!
+ *
+ * Now, the same rules apply as before, except if removing a single level from an unsafe report would make it safe,
+ * the report instead counts as safe.
+ *
+ * More of the above example's reports are now safe:
+ *
+ *   - 7 6 4 2 1: Safe without removing any level.
+ *   - 1 2 7 8 9: Unsafe regardless of which level is removed.
+ *   - 9 7 6 2 1: Unsafe regardless of which level is removed.
+ *   - 1 3 2 4 5: Safe by removing the second level, 3.
+ *   - 8 6 4 4 1: Safe by removing the third level, 4.
+ *   - 1 3 6 7 9: Safe without removing any level.
+ *
+ * Thanks to the Problem Dampener, 4 reports are actually safe!
+ *
+ * Update your analysis by handling situations where the Problem Dampener can remove a single level from unsafe reports.
+ * How many reports are now safe?
+ */
+
+//$count = $reactorReportParser->findSafeReportsCount($reports, true);
+//print('There are ' . $count . " safe reports after applying the Problem Dampener.\n");

2024/inputs/day-02-sample.input

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+7 6 4 2 1
+1 2 7 8 9
+9 7 6 2 1
+1 3 2 4 5
+8 6 4 4 1
+1 3 6 7 9