Solve 2025-04

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;
+}