Solve 2024-04

2024/04/index.ts

@@ -0,0 +1,87 @@
+import { sumArray } from '../../utils/array.ts';
+
+export function solveFirst(input: string): number {
+  const regex = /XMAS/g;
+  const regexBackwards = /SAMX/g;
+
+  const cForwards = [...input.matchAll(regex)].length;
+  const cBackwards = [...input.matchAll(regexBackwards)].length;
+
+  const rows = input.split('\n');
+  const columns = rows.reduce<string[]>((columns, row) => {
+    row
+      .split('')
+      .forEach((char, i) => (columns[i] = (columns[i] || '') + char));
+    return columns;
+  }, []);
+
+  const cColumns = sumArray(
+    columns.map(
+      (column) =>
+        [...column.matchAll(regex), ...column.matchAll(regexBackwards)].length
+    )
+  );
+
+  const rowCount = rows.length - 1;
+
+  const diagonals = rows.reduce<string[]>((diagonals, row, rowIndex) => {
+    row
+      .split('')
+      .forEach(
+        (char, columnIndex) =>
+          (diagonals[columnIndex + (rowCount - rowIndex)] =
+            (diagonals[columnIndex + (rowCount - rowIndex)] || '') + char)
+      );
+    return diagonals;
+  }, []);
+
+  const diagonals2 = rows.reduce<string[]>((diagonals, row, rowIndex) => {
+    row
+      .split('')
+      .forEach(
+        (char, columnIndex) =>
+          (diagonals[columnIndex + rowIndex] =
+            (diagonals[columnIndex + rowIndex] || '') + char)
+      );
+    return diagonals;
+  }, []);
+
+  const cDiagonals = sumArray(
+    diagonals.map(
+      (column) =>
+        [...column.matchAll(regex), ...column.matchAll(regexBackwards)].length
+    )
+  );
+
+  const cDiagonals2 = sumArray(
+    diagonals2.map(
+      (column) =>
+        [...column.matchAll(regex), ...column.matchAll(regexBackwards)].length
+    )
+  );
+
+  return cForwards + cBackwards + cColumns + cDiagonals + cDiagonals2;
+}
+
+export function solveSecond(input: string): number {
+  const rows = input.split('\n');
+
+  const rowCount = rows.length;
+  const columnCount = rows[0].length;
+
+  let found = 0;
+  for (let y = 0; y < rowCount - 2; y++) {
+    for (let x = 0; x < columnCount - 2; x++) {
+      const diag = rows[y][x] + rows[y + 1][x + 1] + rows[y + 2][x + 2];
+      const diag2 = rows[y + 2][x] + rows[y + 1][x + 1] + rows[y][x + 2];
+      if (
+        (diag === 'MAS' || diag === 'SAM') &&
+        (diag2 === 'MAS' || diag2 === 'SAM')
+      ) {
+        found++;
+      }
+    }
+  }
+
+  return found;
+}