day 8

src/day08/README.md

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+# 🎄 Advent of Code 2024 - day 8 🎄
+
+## Info
+
+Task description: [link](https://adventofcode.com/2024/day/8)
+
+## Notes
+
+...

src/day08/index.ts

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+import run from "aocrunner"
+
+const parseInput = (rawInput: string) => rawInput.split('\n').map(line => line.split(''))
+
+const part1 = (rawInput: string) => {
+  const rows = parseInput(rawInput)
+  const towers = new Map<string, string[]>() // 'a' => ['4,5', '7,7'] etc
+  const antinodes = new Set<string>()
+  rows.forEach((row, r) => {
+    row.forEach((char, c) => {
+      if (char === '.') return
+      const towerLocations = towers.get(char) ?? []
+      towerLocations.forEach(locationKey => {
+        const [r2,c2] = locationKey.split(',').map(Number)
+        const newAntinodes = [[2*r2-r, 2*c2-c], [2*r-r2, 2*c-c2]]
+        newAntinodes.forEach(([y, x]) => {
+          if (y < 0 || y >= rows.length || x < 0 || x >= row.length) {
+            return
+          }
+          antinodes.add(`${y},${x}`)
+        })
+      })
+      towerLocations.push(`${r},${c}`)
+      towers.set(char, towerLocations)
+    })
+  })
+  return antinodes.size
+}
+
+const part2 = (rawInput: string) => {
+  const rows = parseInput(rawInput)
+  const towers = new Map<string, string[]>() // 'a' => ['4,5', '7,7'] etc
+  const antinodes = new Set<string>()
+  rows.forEach((row, r) => {
+    row.forEach((char, c) => {
+      if (char === '.') return
+      const towerLocations = towers.get(char) ?? []
+      towerLocations.forEach(locationKey => {
+        const [r2,c2] = locationKey.split(',').map(Number)
+        const slopeTop = c2-c
+        const slopeBottom = r2-r
+        for (let R = 0; R < rows.length; R++) {
+          const dr = R - r
+          const dc = dr * slopeTop / slopeBottom
+          const C = c + dc
+          if (C < 0 || C >= row.length || C % 1 !== 0) {
+            continue
+          }
+          antinodes.add(`${R},${C}`)
+        }
+      })
+      towerLocations.push(`${r},${c}`)
+      towers.set(char, towerLocations)
+    })
+  })
+  return antinodes.size
+}
+
+run({
+  part1: {
+    tests: [
+      {
+        input: `..........
+..........
+..........
+....a.....
+........a.
+.....a....
+..........
+..........
+..........
+..........`,
+        expected: 4
+      },
+      {
+        input: `............
+........0...
+.....0......
+.......0....
+....0.......
+......A.....
+............
+............
+........A...
+.........A..
+............
+............`,
+        expected: 14,
+      },
+    ],
+    solution: part1,
+  },
+  part2: {
+    tests: [
+      {
+        input: `T.........
+...T......
+.T........
+..........
+..........
+..........
+..........
+..........
+..........
+..........`,
+        expected: 9
+      },
+      {
+        input: `............
+........0...
+.....0......
+.......0....
+....0.......
+......A.....
+............
+............
+........A...
+.........A..
+............
+............`,
+        expected: 34,
+      },
+    ],
+    solution: part2,
+  },
+  trimTestInputs: true,
+  onlyTests: false,
+})