day 12

2021/12-input.txt

@@ -0,0 +1,26 @@
+start-YY
+av-rz
+rz-VH
+fh-av
+end-fh
+sk-gp
+ae-av
+YY-gp
+end-VH
+CF-qz
+qz-end
+qz-VG
+start-gp
+VG-sk
+rz-YY
+VH-sk
+rz-gp
+VH-av
+VH-fh
+sk-rz
+YY-sk
+av-gp
+rz-qz
+VG-start
+sk-fh
+VG-av

2021/12.ts

@@ -0,0 +1,48 @@
+import { getInput } from './lib'
+
+const input = getInput(12).map(connection => connection.split('-'))
+
+const part2 = (input) => {
+  let map: Map<string, string[]> = new Map()
+  for (let [from, to] of input) {
+    if (map.has(from)) {
+      map.get(from).push(to)
+    } else {
+      map.set(from, [to])
+    }
+
+    if (map.has(to)) {
+      map.get(to).push(from)
+    } else {
+      map.set(to, [from])
+    }
+  }
+
+  let paths = 0
+  const smallRevisited = (history: string[]) => {
+    let smalls = history.filter(cave => cave === cave.toLowerCase())
+    return smalls.some(small => history.filter(cave => cave === small).length >= 2)
+  }
+
+  const walk = (current: string, history: string[]) => {
+    if (current === 'end') return paths++
+
+    for (let cave of map.get(current)) {
+      if (cave === 'start') continue
+
+      if (
+        cave === cave.toLowerCase()
+        && history.includes(cave)
+        && smallRevisited(history)
+      ) continue
+
+      walk(cave, history.concat(cave))
+    }
+  }
+
+  walk('start', [])
+
+  return paths
+}
+
+console.log(part2(input))