From fa52ced5dd013b14a5341ff9f0194ddc06ca5ad5 Mon Sep 17 00:00:00 2001
From: Nat Lasseter <user@4574.co.uk>
Date: Mon, 4 Dec 2023 12:58:54 +0000
Subject: Day 04

---
 day04/day04.java | 71 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)
 create mode 100644 day04/day04.java

(limited to 'day04/day04.java')

diff --git a/day04/day04.java b/day04/day04.java
new file mode 100644
index 0000000..f803bf9
--- /dev/null
+++ b/day04/day04.java
@@ -0,0 +1,71 @@
+import java.io.IOException;
+import java.io.RandomAccessFile;
+import java.util.Arrays;
+import java.util.ArrayList;
+import java.util.LinkedList;
+import java.util.HashSet;
+import java.util.regex.Pattern;
+import java.util.regex.Matcher;
+
+public class day04 {
+  public static void main(String args[]) throws IOException {
+    RandomAccessFile input = new RandomAccessFile("input", "r");
+    System.out.println("Day 01 Part 1: " + part1(input));
+    input.seek(0);
+    System.out.println("Day 01 Part 2: " + part2(input));
+    input.close();
+  }
+
+  public static String part1(RandomAccessFile input) throws IOException {
+    String line;
+    int tot = 0;
+    while ((line = input.readLine()) != null) {
+      int points = cardMatches(parseCard(line));
+      if (points > 0) {
+        tot += 1 << (points - 1);
+      }
+    }
+
+    return Integer.toString(tot);
+  }
+
+  public static String part2(RandomAccessFile input) throws IOException {
+    ArrayList<String[][]> cards = new ArrayList<>();
+    LinkedList<Integer> queue = new LinkedList<>();
+
+    String line;
+    while ((line = input.readLine()) != null) {
+      cards.add(parseCard(line));
+    }
+
+    for (int i = 0; i < cards.size(); i++) {
+      queue.add(i);
+    }
+
+    int tot = 0;
+    while (queue.size() > 0) {
+      int id = queue.remove();
+      int matches = cardMatches(cards.get(id));
+      for (int i = id + 1; i < id + matches + 1; i++) {
+        queue.add(i);
+      }
+      tot += 1;
+    }
+
+    return Integer.toString(tot);
+  }
+
+  private static String[][] parseCard(String line) {
+    String[] linea = line.split(": +");
+    String[] card = linea[1].split(" \\| +");
+    String[] neednums = card[0].split(" +");
+    String[] havenums = card[1].split(" +");
+    return new String[][]{neednums, havenums};
+  }
+
+  private static int cardMatches(String[][] card) {
+    HashSet<String> winnums = new HashSet<>(Arrays.asList(card[1]));
+    winnums.retainAll(Arrays.asList(card[0]));
+    return winnums.size();
+  }
+}
-- 
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