day 12, part 1 only

src/day12/index.ts

@@ -0,0 +1,185 @@
+import run from "aocrunner"
+
+const parseInput = (rawInput: string) => rawInput.split('\n').map(line => line.split(''))
+
+const directions = [
+  [-1, 0], // up
+  [0, 1], // right
+  [1, 0], // down
+  [0, -1] // left
+]
+const getNeighbors = (r: number, c: number) => {
+  return directions.map(([dr, dc]) => [r + dr, c + dc])
+}
+
+const getKey = (items: unknown[]) => {
+  return items.join(',')
+}
+type Key = ReturnType<typeof getKey>
+
+type Region = {
+  symbol: string
+  area: number
+  perimeter: number
+  plots: Key[]
+}
+
+const part1 = (rawInput: string) => {
+  const input = parseInput(rawInput)
+  let regions = new Set<Region>()
+
+  input.forEach((row, r) => {
+    row.forEach((symbol, c) => {
+      const key = getKey([r, c])
+      const neighbors = getNeighbors(r, c).map(getKey)
+      let touches = 0
+      let matchingRegions: Region[] = []
+      regions.forEach(region => {
+        if (region.symbol !== symbol) return
+        const newTouches = region.plots.filter(c => neighbors.includes(c)).length
+        if (newTouches > 0) {
+          touches += newTouches
+          matchingRegions.push(region)
+          regions.delete(region)
+        }
+      })
+      const newRegion = matchingRegions.reduce<Region>((acc, cur) => {
+        acc.area += cur.area
+        acc.perimeter += cur.perimeter
+        acc.plots.push(...cur.plots)
+        return acc
+      }, {
+        symbol,
+        area: 1,
+        perimeter: 4 - 2 * touches,
+        plots: [key],
+      })
+      regions.add(newRegion)
+    })
+  })
+  return Array.from(regions).reduce((total, region) => total + region.perimeter * region.area, 0)
+}
+
+const part2 = (rawInput: string) => {
+  const input = parseInput(rawInput)
+  let regions = new Set<Region>()
+
+  input.forEach((row, r) => {
+    row.forEach((symbol, c) => {
+      const key = getKey([r, c])
+      const neighbors = getNeighbors(r, c).map(getKey)
+      let touches = 0
+      let matchingRegions: Region[] = []
+      regions.forEach(region => {
+        if (region.symbol !== symbol) return
+        const newTouches = region.plots.filter(c => neighbors.includes(c)).length
+        if (newTouches > 0) {
+          touches += newTouches
+          matchingRegions.push(region)
+          regions.delete(region)
+        }
+      })
+      const newRegion = matchingRegions.reduce<Region>((acc, cur) => {
+        acc.area += cur.area
+        acc.perimeter += cur.perimeter
+        acc.plots.push(...cur.plots)
+        return acc
+      }, {
+        symbol,
+        area: 1,
+        perimeter: 4 - 2 * touches,
+        plots: [key],
+      })
+      regions.add(newRegion)
+    })
+  })
+
+  return Array.from(regions).reduce((total, {
+    symbol,
+    plots,
+    area,
+  }) => {
+    let corners = 0
+    plots.forEach(plot => {
+      const [r, c] = plot.split(',').map(Number)
+      const boundaries = getNeighbors(r, c).map(getKey).map((k, i) => plots.includes(k) ? '' : i).join('')
+      switch(boundaries) {
+        case '0123':
+          corners += 4
+          break
+        case '01':
+        case '12':
+        case '23':
+        case '03':
+          corners += 1
+          break
+        case '012':
+        case '123':
+        case '023':
+        case '013':
+          corners += 2
+          break
+      }
+    })
+    console.log(`Region of ${symbol} with ${corners} sides`)
+    return total + corners * area
+  }, 0)
+}
+
+run({
+//   part1: {
+//     tests: [
+//       {
+//         input: `AAAA
+// BBCD
+// BBCC
+// EEEC`,
+//         expected: 140,
+//       },
+//       {
+//         input: `OOOOO
+// OXOXO
+// OOOOO
+// OXOXO
+// OOOOO`, expected: 772
+//       },
+//       {
+//         input: `RRRRIICCFF
+// RRRRIICCCF
+// VVRRRCCFFF
+// VVRCCCJFFF
+// VVVVCJJCFE
+// VVIVCCJJEE
+// VVIIICJJEE
+// MIIIIIJJEE
+// MIIISIJEEE
+// MMMISSJEEE`,
+//         expected: 1930
+//       }
+//     ],
+//     solution: part1,
+//   },
+  part2: {
+    tests: [
+      {
+        input: `AAAA
+BBCD
+BBCC
+EEEC`,
+        expected: 80,
+      },
+      {
+        input: `AAAAAA
+AAABBA
+AAABBA
+ABBAAA
+ABBAAA
+AAAAAA`,
+        expected: 1206,
+      }
+    ],
+    solution: part2,
+  },
+  trimTestInputs: true,
+  onlyTests: true,
+})