2024 Day 03 part 1 & 2 (#28)

Author: sprak3000

2024/day-03.php

@@ -0,0 +1,76 @@
+<?php
+
+require __DIR__ . '/../vendor/autoload.php';
+
+use adventofcode\Year2024\MultiplyInstructionParser;
+
+/**
+ * --- Day 3: Mull It Over ---
+ *
+ * --- Day 3: Mull It Over ---
+ *
+ * "Our computers are having issues, so I have no idea if we have any Chief Historians in stock! You're welcome to
+ * check the warehouse, though," says the mildly flustered shopkeeper at the North Pole Toboggan Rental Shop. The
+ * Historians head out to take a look.
+ *
+ * The shopkeeper turns to you. "Any chance you can see why our computers are having issues again?"
+ *
+ * The computer appears to be trying to run a program, but its memory (your puzzle input) is corrupted. All of the
+ * instructions have been jumbled up!
+ *
+ * It seems like the goal of the program is just to multiply some numbers. It does that with instructions
+ * like mul(X,Y), where X and Y are each 1-3 digit numbers. For instance, mul(44,46) multiplies 44 by 46 to get a
+ * result of 2024. Similarly, mul(123,4) would multiply 123 by 4.
+ *
+ * However, because the program's memory has been corrupted, there are also many invalid characters that should be
+ * ignored, even if they look like part of a mul instruction. Sequences like mul(4*, mul(6,9!, ?(12,34),
+ * or mul ( 2 , 4 ) do nothing.
+ *
+ * For example, consider the following section of corrupted memory:
+ *
+ * xmul(2,4)%&mul[3,7]!@^do_not_mul(5,5)+mul(32,64]then(mul(11,8)mul(8,5))
+ *
+ * Only the four highlighted sections are real mul instructions. Adding up the result of each instruction
+ * produces 161 (2*4 + 5*5 + 11*8 + 8*5).
+ *
+ * Scan the corrupted memory for uncorrupted mul instructions. What do you get if you add up all of the
+ * results of the multiplications?
+ */
+
+$multiplyInstructionParser = new MultiplyInstructionParser();
+
+$lines = file(__DIR__ . '/inputs/day-03.input', FILE_IGNORE_NEW_LINES);
+
+$sum = $multiplyInstructionParser->findMultiplyInstructionSum($lines);
+print('The sum of the multiplier instructions from the given input is ' . $sum . ".\n");
+
+/**
+ * --- Part Two ---
+ *
+ * As you scan through the corrupted memory, you notice that some of the conditional statements are also still intact.
+ * If you handle some of the uncorrupted conditional statements in the program, you might be able to get an even more
+ * accurate result.
+ *
+ * There are two new instructions you'll need to handle:
+ *
+ *   - The do() instruction enables future mul instructions.
+ *   - The don't() instruction disables future mul instructions.
+ *
+ * Only the most recent do() or don't() instruction applies. At the beginning of the program,
+ * mul instructions are enabled.
+ *
+ * For example:
+ *
+ * xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))
+ *
+ * This corrupted memory is similar to the example from before, but this time the mul(5,5) and mul(11,8) instructions
+ * are disabled because there is a don't() instruction before them. The other mul instructions function normally,
+ * including the one at the end that gets re-enabled by a do() instruction.
+ *
+ * This time, the sum of the results is 48 (2*4 + 8*5).
+ *
+ * Handle the new instructions; what do you get if you add up all of the results of just the enabled multiplications?
+ */
+
+$sum = $multiplyInstructionParser->findExtendedMultiplyInstructionSum($lines);
+print('The sum of the extended multiplier instructions from the given input is ' . $sum . ".\n");

2024/inputs/day-03-sample-part-2.input

@@ -0,0 +1 @@
+xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))

2024/inputs/day-03-sample.input

@@ -0,0 +1 @@
+xmul(2,4)%&mul[3,7]!@^do_not_mul(5,5)+mul(32,64]then(mul(11,8)mul(8,5))