Advent of Code 2023 - Day 3 - Salesforce Apex

Day 3 was traversing a grid of data. Finding certain coordinates based on criteria, and then exploring adjacent coordinates for values. A nice slightly difficult challenge for only Day 3.

--- Day 3: Gear Ratios ---

https://adventofcode.com/2023/day/3

Advent Calendar Progress

Day 03 - Part 1

Day 03 - Part 2

Day 03 - Part 1&2 Solutions

	public with sharing class day03 {
	public static Integer part2(List<String> puzzleInputLines) {
	List<Integer> validGearRatios = new List<Integer>();
	// engine part row
	for(Integer i = 0; i < puzzleInputLines.size(); i++) {
	// engine part columns
	for(Integer col = 0; col < puzzleInputLines[i].length(); col++) {
	String[] columnChars = puzzleInputLines[i].split('');
	// Check if the character is * a gear
	if(isGear(columnChars[col])) {
	Set<Integer> validIndexes = new Set<Integer>();
	// left adjacent start index
	Integer leftAdjacentStartIndex = col - 1;
	// right adjacent end index
	Integer rightAdjacentEndIndex = col + 1;
	// increment to end of current partnumber
	col += 1;
	// get previous row
	String prevRow = i-1 == -1 ? null : puzzleInputLines[i-1];
	// get next row
	String nextRow = i+1 == puzzleInputLines.size() ? null : puzzleInputLines[i+1];
	// find valid indexes
	validIndexes = getIntegerRange(leftAdjacentStartIndex, rightAdjacentEndIndex, puzzleInputLines[i].length());
	// current row, prev row, next row
	Set<Integer> gearRatios = getAdjacentGearRatios(validIndexes, puzzleInputLines[i], prevRow, nextRow);
	if(gearRatios.size() == 2) {
	List<Integer> gearRatiosList = new List<Integer>(gearRatios);
	validGearRatios.add(gearRatiosList[0] * gearRatiosList[1]);
	continue;
	}
	}
	}
	}
	return sumListIntegers(validGearRatios);
	}
	public static Set<Integer> getAdjacentGearRatios(Set<Integer> indexes, String row, String prevRow, String nextRow) {
	Set<Integer> gearRatios = new Set<Integer>();
	for(Integer index : indexes) {
	// current row
	String currentIndexChar = row.split('')[index];
	if(isDigit(currentIndexChar)) {
	gearRatios.add(getFullNumber(index, row));
	}
	if(prevRow != null) {
	// prev row
	String prevIndexChar = prevRow.split('')[index];
	if(isDigit(prevIndexChar)) {
	gearRatios.add(getFullNumber(index, prevRow));
	}
	}
	if(nextRow != null) {
	// next row
	String nextIndexChar = nextRow.split('')[index];
	if(isDigit(nextIndexChar)) {
	gearRatios.add(getFullNumber(index, nextRow));
	}
	}
	}
	return gearRatios;
	}
	public static Integer getFullNumber(Integer foundIndex, String row) {
	// Traverse backward
	String backwardResult = extractDigitsFromString(row, foundIndex, -1);
	// Traverse forward
	String forwardResult = extractDigitsFromString(row, foundIndex + 1, 1);
	return Integer.valueOf(backwardResult + forwardResult);
	}
	private static String extractDigitsFromString(String inputString, Integer startIndex, Integer step) {
	String result = '';
	for(Integer i = startIndex; i >= 0 && i < inputString.length(); i += step) {
	String[] columnChars = inputString.split('');
	// Check if the character is a digit
	if (isDigit(columnChars[i])) {
	// Append the digit to the result
	// backwards
	if(step == -1) {
	result = columnChars[i] + result;
	} else if (step == 1) { // forwards
	result = result + columnChars[i];
	}
	} else {
	// Break the loop if a non-digit character is encountered
	break;
	}
	}
	return result;
	}
	public static Boolean isGear(String ch) {
	return (ch == '*');
	}
	public static Integer part1(List<String> puzzleInputLines) {
	List<Integer> validPartNumbers = new List<Integer>();
	// engine part row
	for(Integer i = 0; i < puzzleInputLines.size(); i++) {
	// engine part columns
	for(Integer col = 0; col < puzzleInputLines[i].length(); col++) {
	String[] columnChars = puzzleInputLines[i].split('');
	// Check if the character is not a letter or a digit
	if(isDigit(columnChars[col])) {
	Set<Integer> validIndexes = new Set<Integer>();
	// left adjacent start index
	Integer leftAdjacentStartIndex = col - 1;
	// parse out the part number
	String partNumber = parsePartNumber(puzzleInputLines[i].substring(col, puzzleInputLines[i].length()));
	// increment to end of current partnumber
	col += partNumber.length()-1;
	Integer rightAdjacentEndIndex = col + 1;
	// find valid indexes
	validIndexes = getIntegerRange(leftAdjacentStartIndex, rightAdjacentEndIndex, puzzleInputLines[i].length());
	// get previous row
	String prevRow = i-1 == -1 ? null : puzzleInputLines[i-1];
	// get next row
	String nextRow = i+1 == puzzleInputLines.size() ? null : puzzleInputLines[i+1];
	Integer valPartNumber = Integer.valueOf(partNumber);
	// current row, prev row, next row
	if(hasAdjacentSymbol(puzzleInputLines[i], validIndexes) ||
	(prevRow != null && hasAdjacentSymbol(prevRow, validIndexes)) ||
	(nextRow != null && hasAdjacentSymbol(nextRow, validIndexes))) {
	validPartNumbers.add(valPartNumber);
	continue;
	}
	}
	}
	}
	return sumListIntegers(validPartNumbers);
	}
	public static Integer sumListIntegers(List<Integer> partNumbers) {
	Integer sum = 0;
	for(Integer value : partNumbers) {
	sum += value;
	}
	return sum;
	}
	public static Boolean hasAdjacentSymbol(String row, Set<Integer> indexes) {
	Boolean isValid = false;
	for(Integer index : indexes) {
	String currentIndexChar = row.split('')[index];
	if(isSymbol(currentIndexChar)) {
	isValid = true;
	break;
	}
	}
	return isValid;
	}
	public static Set<Integer> getIntegerRange(Integer startNumber, Integer endNumber, Integer rowLength) {
	Set<Integer> result = new Set<Integer>();
	for(Integer i = startNumber; i <= endNumber; i++) {
	// check if out of range indexes before adding
	if(i != -1 && i < rowLength) {
	result.add(i);
	}
	}
	return result;
	}
	public static String parsePartNumber(String beginningPartNumber) {
	String partNumber = '';
	for(Integer i = 0; i < beginningPartNumber.length(); i++) {
	if(isDigit(beginningPartNumber.substring(i, i + 1))) {
	partNumber += beginningPartNumber.substring(i, i + 1);
	} else { // end of part number
	break;
	}
	}
	return partNumber;
	}
	public static Boolean isSymbol(String ch) {
	return !isDigit(ch) && ch != '.';
	}
	public static Boolean isDigit(String ch) {
	return (ch >= '0' && ch <= '9');
	}
	}

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Day 03 - complete!