day3part1 works; part2 is maybe a tree-pruning algo?

src/Day03.java

@@ -0,0 +1,73 @@
+package src;
+
+import java.io.FileReader;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Scanner;
+
+public class Day03 {
+    public static void main(String[] args) {
+        part1();
+        part2();
+    }
+
+    private static void part1() {
+        try (Scanner scanner = new Scanner(new FileReader("resources/inputs/03/input"))) {
+            int sum = 0;
+            while (scanner.hasNextLine()) {
+                String raw = scanner.nextLine();
+                List<String> bank = List.of(raw.split(""));
+                int a = 0;
+                int b = 1;
+                int curr = Integer.parseInt(bank.get(a) + bank.get(b));
+                for (int i = 2; i < bank.size(); i++) {
+                    int candidateA = Integer.parseInt(bank.get(a) + bank.get(i));
+                    int candidateB = Integer.parseInt(bank.get(b) + bank.get(i));
+                    if (candidateA > curr) {
+                        curr = candidateA;
+                        b = i;
+                    }
+                    if (candidateB > curr) {
+                        curr = candidateB;
+                        a = b;
+                        b = i;
+                    }
+                }
+                sum += curr;
+            }
+            IO.println(sum);
+        } catch (Exception e) {
+            IO.println(e.getMessage());
+        }
+    }
+
+    private static void part2() {
+        try (Scanner scanner = new Scanner(new FileReader("resources/inputs/03/testinput"))) {
+            long sum = 0L;
+            while (scanner.hasNextLine()) {
+                String raw = scanner.nextLine();
+                List<String> bank = List.of(raw.split(""));
+                // first, get the initial 12 batteries
+                List<String> curr = new ArrayList<>();
+                curr.addAll(bank.subList(0, 12));
+                for (int i = 12; i < bank.size(); i++) {
+                    curr.add(bank.get(i)); // add the next battery to the end of the list
+                    for (int j = 1; j < 10; j++) {
+                        // does the list contain a battery of the specified value?
+                        int index = curr.indexOf(String.valueOf(j));
+                        if (index != -1) {
+                            curr.remove(index); // remove it if it does
+                            break;
+                        }
+                    }
+                }
+                String result = curr.stream().reduce("", String::concat);
+                IO.println(raw + " " + result);
+                sum += Long.parseLong(result);
+            }
+            IO.println(sum);
+        } catch (Exception e) {
+            IO.println(e.getMessage());
+        }
+    }
+}