Solve 2025-07

2025/07/2025-07.run.xml

@@ -0,0 +1,7 @@
+<component name="ProjectRunConfigurationManager">
+  <configuration default="false" name="2025-07" type="BunRunConfiguration">
+    <option name="program" value="2025/07/run.ts" />
+    <option name="workingDirectory" value="$PROJECT_DIR$" />
+    <method v="2" />
+  </configuration>
+</component>

2025/07/index.test.ts

@@ -0,0 +1,27 @@
+import { describe, expect, it } from 'bun:test';
+import { solveFirst, solveSecond } from './index.ts';
+
+describe('2025-07', () => {
+  const testInput = `.......S.......
+...............
+.......^.......
+...............
+......^.^......
+...............
+.....^.^.^.....
+...............
+....^.^...^....
+...............
+...^.^...^.^...
+...............
+..^...^.....^..
+...............
+.^.^.^.^.^...^.
+...............`;
+  it('first', () => {
+    expect(solveFirst(testInput)).toBe(21);
+  });
+  it('second', () => {
+    expect(solveSecond(testInput)).toBe(40);
+  });
+});

2025/07/index.ts

@@ -0,0 +1,51 @@
+import { MultiMap } from '../../utils/multi-map.ts';
+
+export function solveFirst(input: string): number {
+  const rows = input.split('\n');
+  const start = rows[0].indexOf('S');
+
+  const beams = new Set([start]);
+
+  let splits = 0;
+  for (let y = 1; y < rows.length; y++) {
+    const newBeams: number[] = [];
+    beams.forEach((beam) => {
+      if (rows[y][beam] === '.' || beam >= rows[y].length) {
+        return;
+      }
+      if (rows[y][beam] === '^') {
+        splits++;
+        beams.delete(beam);
+        newBeams.push(beam - 1);
+        newBeams.push(beam + 1);
+      }
+    });
+    newBeams.forEach((b) => beams.add(b));
+  }
+
+  return splits;
+}
+
+export function solveSecond(input: string): number {
+  const rows = input.split('\n');
+  const start = rows[0].indexOf('S');
+
+  return solveDown(rows, 1, start);
+}
+
+const cache = new MultiMap<number, [number, number]>();
+function solveDown(map: string[], startY: number, startX: number): number {
+  if (cache.multiHas(startY, startX)) {
+    return cache.multiGet(startY, startX)!;
+  }
+  for (let y = startY; y < map.length; y++) {
+    if (map[y][startX] === '^') {
+      return cache.multiSet(
+        solveDown(map, y + 1, startX - 1) + solveDown(map, y + 1, startX + 1),
+        startY,
+        startX
+      );
+    }
+  }
+  return 1;
+}

2025/07/run.ts

@@ -0,0 +1,12 @@
+import { join } from 'path';
+import { solveFirst, solveSecond } from './index.ts';
+
+const input = await Bun.file(join(__dirname, 'input.txt')).text();
+
+const firstAnswer = solveFirst(input);
+
+console.log(firstAnswer);
+
+const secondAnswer = solveSecond(input);
+
+console.log(secondAnswer);

utils/multi-map.ts

@@ -11,6 +11,18 @@ export class MultiMap<V, K extends unknown[]> extends Map<K[0], any> {
     }
     return this.get(firstKey) as V;
   }
+  multiHas(...keys: K): boolean {
+    const firstKey = keys[0];
+    const otherKeys = keys.slice(1);
+    if (!this.has(firstKey)) {
+      return false;
+    }
+
+    if (otherKeys.length > 0) {
+      return (this.get(firstKey)! as MultiMap<any, any>).multiHas(...otherKeys);
+    }
+    return this.has(firstKey);
+  }
 
   multiSet(value: V, ...keys: K) {
     const firstKey = keys[0];