day 12

src/day12/README.md

@@ -0,0 +1,9 @@
+# 🎄 Advent of Code 2021 - day 12 🎄
+
+## Info
+
+Task description: [link](https://adventofcode.com/2021/day/12)
+
+## Notes
+
+...

src/day12/index.js

@@ -0,0 +1,90 @@
+import run from "aocrunner"
+
+const parseInput = (rawInput) => rawInput.split`\n`.map((x) => x.split`-`)
+
+const part1 = (rawInput) => {
+  let input = parseInput(rawInput)
+  input = input.concat(input.map(([from, to]) => [to, from]))
+  function countPaths(history) {
+    const here = history[history.length - 1]
+    if (here === "end") {
+      //      console.log(history.join`,`)
+      return 1
+    }
+    const exits = [
+      ...input.filter(
+        ([from, to]) =>
+          from === here && (/[A-Z]+/.test(to) || !history.includes(to)),
+      ),
+    ]
+    return exits.reduce(
+      (acc, [from, to]) => acc + countPaths([...history, to]),
+      0,
+    )
+  }
+  return countPaths(["start"])
+}
+
+const part2 = (rawInput) => {
+  let input = parseInput(rawInput)
+  input = input.concat(input.map(([from, to]) => [to, from]))
+  function countPaths(history, haveDoubled = false) {
+    const here = history[history.length - 1]
+    if (here === "end") {
+      // console.log(history.join`,`)
+      return 1
+    }
+    const exits = [
+      ...input.filter(
+        ([from, to]) =>
+          from === here &&
+          to !== "start" &&
+          (!haveDoubled || /[A-Z]+/.test(to) || !history.includes(to)),
+      ),
+    ]
+    return exits.reduce(
+      (acc, [from, to]) =>
+        acc +
+        countPaths(
+          [...history, to],
+          haveDoubled || (/[a-z]+/.test(to) && history.includes(to)),
+        ),
+      0,
+    )
+  }
+  return countPaths(["start"])
+}
+
+run({
+  part1: {
+    tests: [
+      {
+        input: `start-A
+start-b
+A-c
+A-b
+b-d
+A-end
+b-end`,
+        expected: 10,
+      },
+    ],
+    solution: part1,
+  },
+  part2: {
+    tests: [
+      {
+        input: `start-A
+start-b
+A-c
+A-b
+b-d
+A-end
+b-end`,
+        expected: 36,
+      },
+    ],
+    solution: part2,
+  },
+  trimTestInputs: true,
+})