From fed21d417d5cb5df923a756ef8a5672dd8fa633c Mon Sep 17 00:00:00 2001
From: Pascal Syma <p.syma@appfarms.com>
Date: Thu, 4 Dec 2025 10:27:34 +0100
Subject: [PATCH] Solve 2025-04

---
 2025/04/2025-04.run.xml |  7 +++++++
 2025/04/index.test.ts   | 21 +++++++++++++++++++++
 2025/04/index.ts        | 37 +++++++++++++++++++++++++++++++++++++
 2025/04/run.ts          | 12 ++++++++++++
 4 files changed, 77 insertions(+)
 create mode 100644 2025/04/2025-04.run.xml
 create mode 100644 2025/04/index.test.ts
 create mode 100644 2025/04/index.ts
 create mode 100644 2025/04/run.ts

diff --git a/2025/04/2025-04.run.xml b/2025/04/2025-04.run.xml
new file mode 100644
index 0000000..f54ae00
--- /dev/null
+++ b/2025/04/2025-04.run.xml
@@ -0,0 +1,7 @@
+<component name="ProjectRunConfigurationManager">
+  <configuration default="false" name="2025-04" type="BunRunConfiguration">
+    <option name="program" value="2025/04/run.ts" />
+    <option name="workingDirectory" value="$PROJECT_DIR$" />
+    <method v="2" />
+  </configuration>
+</component>
\ No newline at end of file
diff --git a/2025/04/index.test.ts b/2025/04/index.test.ts
new file mode 100644
index 0000000..0829c1d
--- /dev/null
+++ b/2025/04/index.test.ts
@@ -0,0 +1,21 @@
+import { describe, expect, it } from 'bun:test';
+import { solveFirst, solveSecond } from './index.ts';
+
+describe('2025-04', () => {
+  const testInput = `..@@.@@@@.
+@@@.@.@.@@
+@@@@@.@.@@
+@.@@@@..@.
+@@.@@@@.@@
+.@@@@@@@.@
+.@.@.@.@@@
+@.@@@.@@@@
+.@@@@@@@@.
+@.@.@@@.@.`;
+  it('first', () => {
+    expect(solveFirst(testInput)).toBe(13);
+  });
+  it('second', () => {
+    expect(solveSecond(testInput)).toBe(43);
+  });
+});
diff --git a/2025/04/index.ts b/2025/04/index.ts
new file mode 100644
index 0000000..c325b1f
--- /dev/null
+++ b/2025/04/index.ts
@@ -0,0 +1,37 @@
+import { replaceChar } from '../../utils/array.ts';
+import { findCoordsOfDigit, getAdjacent } from '../../utils/coordinates.ts';
+
+const PAPER_ROLL = '@';
+export function solveFirst(input: string): number {
+  const rows = input.split('\n');
+
+  const rolls = findCoordsOfDigit(rows, PAPER_ROLL).filter(
+    ([x, y]) =>
+      Object.values(getAdjacent(rows, x, y)).filter((n) => n === PAPER_ROLL)
+        .length < 4
+  );
+  return rolls.length;
+}
+
+export function solveSecond(input: string): number {
+  const rows = input.split('\n');
+
+  let removed = 0;
+
+  let removedInStep = 0;
+  do {
+    removedInStep = 0;
+    findCoordsOfDigit(rows, PAPER_ROLL).forEach(([x, y]) => {
+      if (
+        Object.values(getAdjacent(rows, x, y)).filter((n) => n === PAPER_ROLL)
+          .length < 4
+      ) {
+        removedInStep++;
+        replaceChar(rows, x, y, 'X');
+      }
+    });
+    removed += removedInStep;
+  } while (removedInStep > 0);
+
+  return removed;
+}
diff --git a/2025/04/run.ts b/2025/04/run.ts
new file mode 100644
index 0000000..88783cd
--- /dev/null
+++ b/2025/04/run.ts
@@ -0,0 +1,12 @@
+import { join } from 'path';
+import { solveFirst, solveSecond } from './index.ts';
+
+const input = await Bun.file(join(__dirname, 'input.txt')).text();
+
+const firstAnswer = solveFirst(input);
+
+console.log(firstAnswer);
+
+const secondAnswer = solveSecond(input);
+
+console.log(secondAnswer);