day 10

src/day10/README.md

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+# 🎄 Advent of Code 2024 - day 10 🎄
+
+## Info
+
+Task description: [link](https://adventofcode.com/2024/day/10)
+
+## Notes
+
+...

src/day10/index.ts

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+import run from "aocrunner"
+
+const parseInput = (rawInput: string) => rawInput.split('\n').map(line => line.split('').map(Number))
+
+const directions = [
+  [-1, 0], // up
+  [0, 1], // right
+  [1, 0], // down
+  [0, -1] // left
+]
+
+const sum = (a,b) => a + b
+
+const getKey = (r: number, c: number) => `${r},${c}`
+type Key = ReturnType<typeof getKey>
+
+const part1 = (rawInput: string) => {
+  const input = parseInput(rawInput)
+  const trailheads: Key[] = []
+  const exitsMap = new Map<Key, Key[]>()
+  const get = (r: number, c: number) => {
+    return (input[r] ?? [])[c]
+  }
+  input.forEach((row, r) => {
+    row.forEach((alt, c) => {
+      const key = getKey(r, c)
+      if (alt === 0) {
+        trailheads.push(key)
+      }
+      const outs: Key[] = []
+      directions.forEach(([dr, dc]) => {
+        if (get(r + dr, c + dc) === alt + 1) {
+          outs.push(getKey(r + dr, c + dc))
+        }
+      })
+      exitsMap.set(key, outs)
+    })
+  })
+  const reachablePeaks = new Map<Key, Set<Key>>()
+  const hike = (key: Key, alt: number = 0): Set<Key> => {
+    let ans = reachablePeaks.get(key)
+    if (ans !== undefined) return ans
+    ans = new Set<Key>()
+    if (alt === 9) {
+      ans.add(key)
+      reachablePeaks.set(key, ans)
+      return ans
+    }
+    const branches = (exitsMap.get(key) ?? []).map(k => hike(k,alt+1))
+    branches.forEach(peaks => {
+      peaks.forEach(peak => ans.add(peak))
+    })
+    reachablePeaks.set(key, ans)
+    return ans
+  }
+  return trailheads.map(t => hike(t).size).reduce(sum, 0)
+}
+
+const part2 = (rawInput: string) => {
+  const input = parseInput(rawInput)
+  const trailheads: Key[] = []
+  const exitsMap = new Map<Key, Key[]>()
+  const get = (r: number, c: number) => {
+    return (input[r] ?? [])[c]
+  }
+  input.forEach((row, r) => {
+    row.forEach((alt, c) => {
+      const key = getKey(r, c)
+      if (alt === 0) {
+        trailheads.push(key)
+      }
+      const outs: Key[] = []
+      directions.forEach(([dr, dc]) => {
+        if (get(r + dr, c + dc) === alt + 1) {
+          outs.push(getKey(r + dr, c + dc))
+        }
+      })
+      exitsMap.set(key, outs)
+    })
+  })
+  const cache = new Map<Key, number>()
+  const hike = (key: Key, alt: number): number => {
+    if (alt === 9) {
+      return 1
+    }
+    let ans = cache.get(key)
+    if (ans !== undefined) return ans
+    const exitTotals = (exitsMap.get(key) ?? []).map(k => hike(k,alt+1))
+    ans = exitTotals.reduce(sum, 0)
+    cache.set(key, ans)
+    return ans
+  }
+  return trailheads.map(t => hike(t,0)).reduce(sum, 0)
+}
+
+run({
+  part1: {
+    tests: [
+      {
+        input: `0123
+1234
+8765
+9876`,
+        expected: 1,
+      },
+    ],
+    solution: part1,
+  },
+  part2: {
+    tests: [
+      {
+        input: `012345
+123456
+234567
+345678
+4.6789
+56789.`,
+expected: 227
+      },
+      {
+        input: `89010123
+78121874
+87430965
+96549874
+45678903
+32019012
+01329801
+10456732`,
+        expected: 81,
+      },
+    ],
+    solution: part2,
+  },
+  trimTestInputs: true,
+  onlyTests: false,
+})