just needed to be smarter about which batteries were valuable to remove

src/Day03.java

@@ -42,7 +42,7 @@ public class Day03 {
     }
 
     private static void part2() {
-        try (Scanner scanner = new Scanner(new FileReader("resources/inputs/03/testinput"))) {
+        try (Scanner scanner = new Scanner(new FileReader("resources/inputs/03/input"))) {
             long sum = 0L;
             while (scanner.hasNextLine()) {
                 String raw = scanner.nextLine();
@@ -52,17 +52,16 @@ public class Day03 {
                 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;
-                        }
+                    // find the smallest battery in the list that's ahead of a larger battery
+                    int t1 = 0;
+                    int t2 = 1;
+                    while (t2 < curr.size() && Integer.parseInt(curr.get(t1)) >= Integer.parseInt(curr.get(t2))) {
+                        t1++;
+                        t2++;
                     }
+                    curr.remove(t1);
                 }
                 String result = curr.stream().reduce("", String::concat);
-                IO.println(raw + " " + result);
                 sum += Long.parseLong(result);
             }
             IO.println(sum);