Add coordinate utils

utils/coordinates.test.ts

@@ -1,5 +1,11 @@
 import { describe, expect, it } from 'bun:test';
-import { type Coordinate, inBounds, isCoordinateEqual } from './coordinates.ts';
+import {
+  type Coordinate,
+  findCoordsOfDigit,
+  getAdjacent,
+  inBounds,
+  isCoordinateEqual
+} from './coordinates.ts';
 
 describe('coordinates utils', () => {
   it('inBounds', () => {
@@ -30,4 +36,69 @@ describe('coordinates utils', () => {
     expect(isCoordinateEqual(b, b)).toBeTrue();
     expect(isCoordinateEqual(a, b)).toBeTrue();
   });
+
+  it('getAdjacent', () => {
+    const input = `0123
+1234
+8765
+9876`.split('\n');
+
+    const actualTopLeft = getAdjacent(input, 0, 0);
+
+    expect(actualTopLeft).toBeObject();
+    expect(Object.keys(actualTopLeft)).toHaveLength(8);
+    expect(actualTopLeft.top).toBeUndefined();
+    expect(actualTopLeft.topRight).toBeUndefined();
+    expect(actualTopLeft.right).toEqual('1');
+    expect(actualTopLeft.downRight).toEqual('2');
+    expect(actualTopLeft.down).toEqual('1');
+    expect(actualTopLeft.downLeft).toBeUndefined();
+    expect(actualTopLeft.left).toBeUndefined();
+    expect(actualTopLeft.topLeft).toBeUndefined();
+
+    const actualFirst7 = getAdjacent(input, 1, 2);
+
+    expect(actualFirst7).toBeObject();
+    expect(Object.keys(actualFirst7)).toHaveLength(8);
+    expect(actualFirst7.top).toEqual('2');
+    expect(actualFirst7.topRight).toEqual('3');
+    expect(actualFirst7.right).toEqual('6');
+    expect(actualFirst7.downRight).toEqual('7');
+    expect(actualFirst7.down).toEqual('8');
+    expect(actualFirst7.downLeft).toEqual('9');
+    expect(actualFirst7.left).toEqual('8');
+    expect(actualFirst7.topLeft).toEqual('1');
+  });
+
+  it('findCoordsOfDigit', () => {
+    const input = `0123
+1234
+8765
+9876`.split('\n');
+    const actualZero = findCoordsOfDigit(input, '0');
+
+    expect(actualZero).toBeArray();
+    expect(actualZero).toHaveLength(1);
+    actualZero.forEach((coord) => expect(coord).toBeArray());
+    actualZero.forEach((coord) => expect(coord).toBeArrayOfSize(2));
+    expect(actualZero[0]).toEqual([0, 0]);
+
+    const actualSeven = findCoordsOfDigit(input, '7');
+
+    expect(actualSeven).toBeArray();
+    expect(actualSeven).toHaveLength(2);
+    actualSeven.forEach((coord) => expect(coord).toBeArray());
+    actualSeven.forEach((coord) => expect(coord).toBeArrayOfSize(2));
+    expect(actualSeven[0]).toEqual([1, 2]);
+    expect(actualSeven[1]).toEqual([2, 3]);
+
+    const actualSevenRegex = findCoordsOfDigit(input, /7/g);
+
+    expect(actualSevenRegex).toBeArray();
+    expect(actualSevenRegex).toHaveLength(2);
+    actualSevenRegex.forEach((coord) => expect(coord).toBeArray());
+    actualSevenRegex.forEach((coord) => expect(coord).toBeArrayOfSize(2));
+    expect(actualSevenRegex[0]).toEqual([1, 2]);
+    expect(actualSevenRegex[1]).toEqual([2, 3]);
+  });
 });

utils/coordinates.ts

@@ -24,3 +24,57 @@ export function isCoordinateEqual(
 ): boolean {
   return b[0] === a[0] && b[1] === a[1];
 }
+
+export type DirectNeighbours = 'top' | 'left' | 'right' | 'down';
+
+export type DiagonalNeighbours =
+  | 'topLeft'
+  | 'topRight'
+  | 'downLeft'
+  | 'downRight';
+
+/**
+ * Get all eight adjacent cells from a starting cell.
+ * Returns undefined, when the cell is invalid (out of bounds).
+ * @param rows Input xy-Matrix, string array
+ * @param startX Center cell x Coordinate
+ * @param startY Center cell y Coordinate
+ */
+export function getAdjacent(
+  rows: string[],
+  startX: number,
+  startY: number
+): Record<DirectNeighbours | DiagonalNeighbours, string | undefined> {
+  const top = rows[startY - 1]?.[startX];
+  const right = rows[startY]?.[startX + 1];
+  const down = rows[startY + 1]?.[startX];
+  const left = rows[startY]?.[startX - 1];
+
+  const topLeft = rows[startY - 1]?.[startX - 1];
+  const topRight = rows[startY - 1]?.[startX + 1];
+  const downLeft = rows[startY + 1]?.[startX - 1];
+  const downRight = rows[startY + 1]?.[startX + 1];
+
+  return { top, right, left, down, topLeft, topRight, downLeft, downRight };
+}
+
+/**
+ * Find all xy-Coordinates of a digit or custom regex match.
+ * @param rows Input xy-Matrix, string array
+ * @param digit Digit to search for, or custom regex pattern
+ */
+export function findCoordsOfDigit(
+  rows: string[],
+  digit: string | RegExp
+): Coordinates {
+  return rows.reduce<Coordinates>(
+    (coords, row, y) =>
+      row
+        .matchAll(typeof digit === 'string' ? new RegExp(digit, 'g') : digit)
+        .reduce(
+          (coordinates, m) => [...coordinates, [m.index, y] as Coordinate],
+          coords
+        ),
+    []
+  );
+}