solved part 1 with gaus

src/advent-of-code-solver/2023/day-18/__tests__/gauss-area-formula.test.ts

@@ -0,0 +1,46 @@
+import { Coordinate } from '../../../common/matrix/interface';
+import { findArea } from '../gauss-area-formula';
+
+describe('findArea', () => {
+  let coordinates: Coordinate[];
+  describe('a four corner polygon starting at x:0, y:0', () => {
+    beforeEach(() => {
+      coordinates = [
+        { x: 0, y: 0 },
+        { x: 0, y: 3 },
+        { x: 7, y: 3 },
+        { x: 7, y: 0 },
+      ];
+    });
+    it('should return 14', () => {
+      expect(findArea(coordinates)).toEqual(21);
+    });
+  });
+  describe('an offset four corner polygon', () => {
+    beforeEach(() => {
+      coordinates = [
+        { x: 1, y: 0 },
+        { x: 7, y: 0 },
+        { x: 7, y: 3 },
+        { x: 1, y: 3 },
+      ];
+    });
+    it('should return 18', () => {
+      expect(findArea(coordinates)).toEqual(18);
+    });
+  });
+  describe('a five corner polygon', () => {
+    beforeEach(() => {
+      coordinates = [
+        { x: 2, y: 7 },
+        { x: 10, y: 1 },
+        { x: 8, y: 6 },
+        { x: 11, y: 7 },
+        { x: 7, y: 10 },
+      ];
+    });
+    it('should return 18', () => {
+      expect(findArea(coordinates)).toEqual(32);
+    });
+  });
+});

src/advent-of-code-solver/2023/day-18/__tests__/solver.test.ts

@@ -4,51 +4,60 @@ import LavaductLagoonSolver, { DigInstruction } from '../solver';
 describe('day 18', () => {
   let solver: Solver<DigInstruction[]>;
   describe('part one', () => {
-    type TestCase = { input: string; output: number };
-    const cases: TestCase[] = [
-      {
-        input:
-          'R 6 (#70c710)\n' +
-          'D 5 (#0dc571)\n' +
-          'L 2 (#5713f0)\n' +
-          'D 2 (#d2c081)\n' +
-          'R 2 (#59c680)\n' +
-          'D 2 (#411b91)\n' +
-          'L 5 (#8ceee2)\n' +
-          'U 2 (#caa173)\n' +
-          'L 1 (#1b58a2)\n' +
-          'U 2 (#caa171)\n' +
-          'R 2 (#7807d2)\n' +
-          'U 3 (#a77fa3)\n' +
-          'L 2 (#015232)\n' +
-          'U 2 (#7a21e3)\n',
-        output: 62,
-      },
-      {
-        input:
-          'U 1 (#70c710)\n' +
-          'R 6 (#70c710)\n' +
-          'D 6 (#0dc571)\n' +
-          'L 2 (#5713f0)\n' +
-          'D 2 (#d2c081)\n' +
-          'R 2 (#59c680)\n' +
-          'D 2 (#411b91)\n' +
-          'L 5 (#8ceee2)\n' +
-          'U 2 (#caa173)\n' +
-          'L 1 (#1b58a2)\n' +
-          'U 2 (#caa171)\n' +
-          'R 2 (#7807d2)\n' +
-          'U 3 (#a77fa3)\n' +
-          'L 2 (#015232)\n' +
-          'U 2 (#7a21e3)\n',
-        output: 69,
-      },
-    ];
-    describe.each(cases)('with input $input', ({ input, output }: TestCase) => {
-      it(`should equal to ${output}`, () => {
-        solver = new LavaductLagoonSolver(input);
+    describe('box', () => {
+      it(`should equal`, () => {
+        solver = new LavaductLagoonSolver('R 2 (#70c710)\n' + 'D 1 (#0dc571)\n' + 'L 2 (#5713f0)\n' + 'U 1 (#d2c081)\n');
         const result = solver.solvePartOne();
-        expect(result).toEqual(output);
+        expect(result).toEqual(6);
+      });
+    });
+    describe('sample-data', () => {
+      type TestCase = { input: string; output: number };
+      const cases: TestCase[] = [
+        {
+          input:
+            'R 6 (#70c710)\n' +
+            'D 5 (#0dc571)\n' +
+            'L 2 (#5713f0)\n' +
+            'D 2 (#d2c081)\n' +
+            'R 2 (#59c680)\n' +
+            'D 2 (#411b91)\n' +
+            'L 5 (#8ceee2)\n' +
+            'U 2 (#caa173)\n' +
+            'L 1 (#1b58a2)\n' +
+            'U 2 (#caa171)\n' +
+            'R 2 (#7807d2)\n' +
+            'U 3 (#a77fa3)\n' +
+            'L 2 (#015232)\n' +
+            'U 2 (#7a21e3)\n',
+          output: 62,
+        },
+        {
+          input:
+            'U 1 (#70c710)\n' +
+            'R 6 (#70c710)\n' +
+            'D 6 (#0dc571)\n' +
+            'L 2 (#5713f0)\n' +
+            'D 2 (#d2c081)\n' +
+            'R 2 (#59c680)\n' +
+            'D 2 (#411b91)\n' +
+            'L 5 (#8ceee2)\n' +
+            'U 2 (#caa173)\n' +
+            'L 1 (#1b58a2)\n' +
+            'U 2 (#caa171)\n' +
+            'R 2 (#7807d2)\n' +
+            'U 3 (#a77fa3)\n' +
+            'L 2 (#015232)\n' +
+            'U 2 (#7a21e3)\n',
+          output: 69,
+        },
+      ];
+      describe.each(cases)('with input $input', ({ input, output }: TestCase) => {
+        it(`should equal to ${output}`, () => {
+          solver = new LavaductLagoonSolver(input);
+          const result = solver.solvePartOne();
+          expect(result).toEqual(output);
+        });
       });
     });
   });
@@ -70,7 +79,7 @@ describe('day 18', () => {
           'R 2 (#7807d2)\n' +
           'U 3 (#a77fa3)\n' +
           'L 2 (#015232)\n' +
-          'U 2 (#7a21e3)\n',
+          'U 2 (#7a21e3)',
         output: 952408144115,
       },
     ];

src/advent-of-code-solver/2023/day-18/gauss-area-formula.ts

@@ -0,0 +1,22 @@
+import { summarize } from '../../common/array-operations/reduce';
+import { Coordinate } from '../../common/matrix/interface';
+
+/**
+ * Gauss area formula aka the Shoelace formula
+ * https://en.wikipedia.org/wiki/Shoelace_formula
+ */
+export function findArea(coordinates: Coordinate[]): number {
+  const shoelace_a = calculateSum(coordinates, (coordinate, i) => coordinate.x * nextCoordinate(coordinates, i).y);
+  const shoelace_b = calculateSum(coordinates, (coordinate, i) => coordinate.y * nextCoordinate(coordinates, i).x);
+  console.log(`shoelace_a: ${shoelace_a}`);
+  console.log(`shoelace_b: ${shoelace_b}`);
+  return Math.abs(shoelace_a - shoelace_b) / 2;
+}
+function nextCoordinate(coordinates: Coordinate[], i: number) {
+  return coordinates[(i + 1) % coordinates.length];
+}
+
+function calculateSum(coordinates: Coordinate[], mapFn: (_coordinate: Coordinate, index: number) => number) {
+  const sums = coordinates.map(mapFn);
+  return sums.reduce(summarize, 0);
+}