day 3 initial solution

src/2023/day03.js

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+function signed(map, i, j) {
+  const neighbors = [
+    map[i - 1]?.[j - 1],
+    map[i - 1]?.[j],
+    map[i - 1]?.[j + 1],
+    map[i]?.[j - 1],
+    map[i]?.[j + 1],
+    map[i + 1]?.[j - 1],
+    map[i + 1]?.[j],
+    map[i + 1]?.[j + 1],
+  ];
+  return neighbors.some(n => n !== '.' && (n < '0' || n > '9'));
+}
+
+function gear(map, i, j) {
+  const neighbors = [
+    { x: i - 1, y: j - 1, c: map[i - 1]?.[j - 1] },
+    { x: i - 1, y: j, c: map[i - 1]?.[j] },
+    { x: i - 1, y: j + 1, c: map[i - 1]?.[j + 1] },
+    { x: i, y: j - 1, c: map[i]?.[j - 1] },
+    { x: i, y: j + 1, c: map[i]?.[j + 1] },
+    { x: i + 1, y: j - 1, c: map[i + 1]?.[j - 1] },
+    { x: i + 1, y: j, c: map[i + 1]?.[j] },
+    { x: i + 1, y: j + 1, c: map[i + 1]?.[j + 1] },
+  ];
+  const gears = neighbors.filter(n => n.c === '*');
+  if (gears.length > 1) {
+    console.log(gears); //?
+  }
+  return gears.length === 0 ? undefined : `${gears[0].x},${gears[0].y}`;
+}
+
+export function part1(input) {
+  const map = input.split('\n').map(line => line.split(''));
+  let current = '';
+  let sign = false;
+  let sum = 0;
+  for (let i = 0; i < map.length; i++) {
+    const line = map[i];
+    for (let j = 0; j < line.length; j++) {
+      const char = line[j];
+      if (char >= '0' && char <= '9') {
+        current += char;
+        if (signed(map, i, j)) {
+          sign = true;
+        }
+      } else {
+        if (current) {
+          if (sign) sum += +current;
+          current = '';
+          sign = false;
+        }
+      }
+    }
+    if (current) {
+      if (sign) sum += +current;
+      current = '';
+      sign = false;
+    }
+  }
+  return sum;
+}
+
+export function part2(input) {
+  const map = input.split('\n').map(line => line.split(''));
+  let current = '';
+  let pos = undefined;
+  let gears = {};
+  for (let i = 0; i < map.length; i++) {
+    const line = map[i];
+    for (let j = 0; j < line.length; j++) {
+      const char = line[j];
+      if (char >= '0' && char <= '9') {
+        current += char;
+        pos = pos || gear(map, i, j);
+      } else {
+        if (current) {
+          if (pos)
+            gears[pos] = gears[pos] ? gears[pos].concat(current) : [+current];
+          current = '';
+          pos = undefined;
+        }
+      }
+    }
+    if (current) {
+      if (pos)
+        gears[pos] = gears[pos] ? gears[pos].concat(current) : [+current];
+      current = '';
+      pos = undefined;
+    }
+  }
+  gears = Object.values(gears).map(gear => {
+    if (gear.length > 1) {
+      return gear.reduce((a, b) => a * b, 1);
+    } else {
+      return 0;
+    }
+  });
+  return Object.values(gears).reduce((a, b) => a + b, 0);
+}

src/2023/day03.spec.js

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+import { part1, part2 } from './day03.js';
+import readInput from '../utils/read-input.js';
+
+const input = readInput(import.meta.url);
+
+describe('day03 2023', () => {
+  describe('part1', () => {
+    it('should work for part 1 examples', () => {
+      expect(
+        part1(
+          [
+            '467..114..',
+            '...*......',
+            '..35..633.',
+            '......#...',
+            '617*......',
+            '.....+.58.',
+            '..592.....',
+            '......755.',
+            '...$.*....',
+            '.664.598..',
+          ].join('\n'),
+        ),
+      ).toEqual(4361);
+    });
+
+    it('should work for part 1 input', () => {
+      expect(part1(input)).toEqual(528799);
+    });
+  });
+
+  describe('part2', () => {
+    it('should work for part 2 examples', () => {
+      expect(
+        part2(
+          [
+            '467..114..',
+            '...*......',
+            '..35..633.',
+            '......#...',
+            '617*......',
+            '.....+.58.',
+            '..592.....',
+            '......755.',
+            '...$.*....',
+            '.664.598..',
+          ].join('\n'),
+        ),
+      ).toEqual(467835);
+    });
+
+    it('should work for part 2 input', () => {
+      expect(part2(input)).toEqual(84907174);
+    });
+  });
+});