Je me lance ma soluce en Java

Un peu long à coder, j'ai passé plus de temps sur la première partie que sur la deuxième partie.

Partie 1 :

public class Aoc2023s3p1 {
 public static void main(String[] args) {
 try(Scanner in = new Scanner(Aoc2023s3p1.class.getResourceAsStream("res/Aoc2023s3p1.txt"))) {
 String row;
 int sum =0;
 List<String> rows = new ArrayList<>();
 while(in.hasNext()) {
 row = in.nextLine();
 rows.add(row);
 }
 for(int x=0;x < rows.size();x++) {
 sum += check(x, rows);
 }
 System.out.println(sum);
 }
 }
 public static record Num(int start, int end, String data) {
 }
 public static int check(int rowIndex, List<String> rows) {
 String row = rows.get(rowIndex);
 List<Num> list = new ArrayList<>();
 Integer start = null;
 for(int x=0;x < row.length();x++) {
 int c = row.charAt(x) - '0';
 if(Character.isDigit(row.charAt(x))) {
 if(start == null) {
 start = x;
 }
 } else {
 if(start != null) {
 list.add(new Num(start, x, row.substring(start, x)));
 start = null;
 }
 }
 }
 if(start !=null) {
 list.add(new Num(start, row.length(), row.substring(start)));
 }
 int sum = 0;
 for(Num num : list) {
 System.out.println(num);
 if(checkNum(num, rowIndex, rows)) {
 System.out.println("OK");
 sum += Integer.parseInt(num.data());
 }
 }
 return sum;
 }
 private static boolean checkNum(Num num, int rowIndex, List<String> rows) {
 int before = num.start-1;
 if(checkCharacter(rowIndex, before, rows)) {
 return true; 
 }
 if(checkCharacter(rowIndex, num.end, rows)) {
 return true; 
 }
 for(int x = num.start-1;x < num.end+1;x++) {
 if(checkCharacter(rowIndex - 1, x, rows)
 || checkCharacter(rowIndex + 1, x, rows)) {
 return true;
 }
 }
 return false;
 }
 private static boolean checkCharacter(int rowIndex, int colIndex, List<String> rows) {
 if(rowIndex < 0 || rowIndex >= rows.size()) {
 return false;
 }
 String row = rows.get(rowIndex);
 if(colIndex < 0 || colIndex >= row.length()) {
 return false;
 }
 char c = row.charAt(colIndex);
 if(Character.isDigit(c) || c == '.') {
 return false;
 }
 return true;
 }
}

Pour la partie 2, l'idée est assez simple. J'identifie les engrenages '*' par leurs coordonnées et je stocke sur chaque coordonnée la liste des nombres associés (numsById)

public class Aoc2023s3p2 {
 public static Map<Coord, List<Num>> numsById = new HashMap<>();
 public static void main(String[] args) {
 try(Scanner in = new Scanner(Aoc2023s3p2.class.getResourceAsStream("res/Aoc2023s3p1.txt"))) {
 String row;
 List<String> rows = new ArrayList<>();
 while(in.hasNext()) {
 row = in.nextLine();
 rows.add(row);
 }
 for(int x=0;x < rows.size();x++) {
 check(x, rows);
 }
 int sum =0;
 for(List<Num> nums: numsById.values()) {
 if(nums.size() <= 1) {
 continue;
 }
 System.out.println("=====");
 int prod = 1;
 for(Num num : nums) {
 prod *= Integer.parseInt(num.data);
 System.out.println(num.data);
 }
 System.out.println("=>" + prod);
 sum += prod;
 }
 System.out.println(sum);
 }
 }
 public static record Num(int start, int end, String data) {
 }
 public static void check(int rowIndex, List<String> rows) {
 String row = rows.get(rowIndex);
 List<Num> list = new ArrayList<>();
 Integer start = null;
 for(int x=0;x < row.length();x++) {
 int c = row.charAt(x) - '0';
 if(Character.isDigit(row.charAt(x))) {
 if(start == null) {
 start = x;
 }
 } else {
 if(start != null) {
 list.add(new Num(start, x, row.substring(start, x)));
 start = null;
 }
 }
 }
 if(start !=null) {
 list.add(new Num(start, row.length(), row.substring(start)));
 }
 for(Num num : list) {
 System.out.println(num);
 if(isGearPart(num, rowIndex, rows)) {
 System.out.println("OK");
 }
 }
 }
 private static boolean isGearPart(Num num, int rowIndex, List<String> rows) {
 int before = num.start-1;
 checkGear(num, rowIndex, before, rows);
 checkGear(num, rowIndex, num.end, rows);
 for(int x = num.start-1;x < num.end+1;x++) {
 checkGear(num, rowIndex - 1, x, rows);
 checkGear(num, rowIndex + 1, x, rows);
 }
 return false;
 }
 public static record Coord(int rowIndex, int colIndex) {
 }
 private static boolean checkGear(Num num, int rowIndex, int colIndex, List<String> rows) {
 if(rowIndex < 0 || rowIndex >= rows.size()) {
 return false;
 }
 String row = rows.get(rowIndex);
 if(colIndex < 0 || colIndex >= row.length()) {
 return false;
 }
 char c = row.charAt(colIndex);
 if(c == '*') {
 numsById.computeIfAbsent(new Coord(rowIndex, colIndex),k->new ArrayList<>()).add(num);
 }
 return false;
 }
}