day 16 completed!

.aocrunner.json

@@ -245,10 +245,10 @@
         "time": null
       },
       "part2": {
-        "solved": false,
-        "result": null,
+        "solved": true,
+        "result": "631",
         "attempts": [],
-        "time": null
+        "time": 132.54635
       }
     },
     {

README.md

@@ -26,7 +26,7 @@
 [![Day](https://badgen.net/badge/13/%E2%98%85%E2%98%85/green)](src/day13)
 [![Day](https://badgen.net/badge/14/%E2%98%85%E2%98%86/yellow)](src/day14)
 [![Day](https://badgen.net/badge/15/%E2%98%85%E2%98%85/green)](src/day15)
-[![Day](https://badgen.net/badge/16/%E2%98%85%E2%98%86/yellow)](src/day16)
+[![Day](https://badgen.net/badge/16/%E2%98%85%E2%98%85/green)](src/day16)
 ![Day](https://badgen.net/badge/17/%E2%98%86%E2%98%86/gray)
 ![Day](https://badgen.net/badge/18/%E2%98%86%E2%98%86/gray)
 ![Day](https://badgen.net/badge/19/%E2%98%86%E2%98%86/gray)
@@ -174,9 +174,9 @@ Both parts: 111802.997ms
 
 ```
 Day 16
-Time part 1: 88.714ms
-Time part 2: -
-Both parts: 88.714ms
+Time part 1: -
+Time part 2: 132.546ms
+Both parts: 132.546ms
 ```
 
 ```
@@ -243,8 +243,8 @@ Both parts: -
 ```
 
 ```
-Total stars: 30/50
-Total time: 150797.381ms
+Total stars: 31/50
+Total time: 150841.213ms
 ```
 
 <!--/RESULTS-->

src/day16/index.ts

@@ -26,7 +26,6 @@ type Step = {
 
 const part1 = (rawInput: string) => {
   const input = parseInput(rawInput)
-  const get = (r: number, c: number) => (input[r] ?? [])[c]
   const startIndex = rawInput.indexOf('S')
   const c0 = startIndex % (input[0].length + 1)
   const r0 = (startIndex - c0) / (input[0].length + 1)
@@ -42,38 +41,38 @@ const part1 = (rawInput: string) => {
   while (pq.size() > 0) {
     const prev = pq.pop()
     const { r, c, dir, cost } = prev
-    const here = get(r, c)
+    const here = input[r][c]
     if (here === 'E') {
-      // draw it
-      let cur = prev
-      const visited = new Map<string, number>()
-      while (cur.prev.prev !== null) {
-        visited.set(`${cur.prev.r},${cur.prev.c}`, cur.dir)
-        cur = cur.prev
-      }
-      console.log(
-        input
-          .map((row, r2) => {
-            return row
-              .map((cell, c2) => {
-                const key = `${r2},${c2}`
-                if (visited.has(key)) return bold(">v<^"[visited.get(key)])
-                if (cell === "#") return "\x1b[100m \x1b[0m"
-                if (cell === ".") return " "
-                return `\x1b[41m${cell}\x1b[0m`
-              })
-              .join("")
-          })
-          .join("\n"),
-      )
-      // done drawing
+      { // draw it
+        let cur = prev
+        const visited = new Map<string, number>()
+        while (cur.prev.prev !== null) {
+          visited.set(`${cur.prev.r},${cur.prev.c}`, cur.dir)
+          cur = cur.prev
+        }
+        console.log(
+          input
+            .map((row, r2) => {
+              return row
+                .map((cell, c2) => {
+                  const key = `${r2},${c2}`
+                  if (visited.has(key)) return bold(">v<^"[visited.get(key)])
+                  if (cell === "#") return "\x1b[100m \x1b[0m"
+                  if (cell === ".") return " "
+                  return `\x1b[41m${cell}\x1b[0m`
+                })
+                .join("")
+            })
+            .join("\n"),
+        )
+      } // done drawing
       return cost
     }
     for (let i = 0; i < (here === "S" ? 4 : 3); i += 1) {
       const newDir = (dir + 3 + i) % 4 // left, ahead, right, u-turn
       const [dr, dc] = deltas[newDir]
       const addedCost = [1001, 1, 1001, 2001][i]
-      if (get(r + dr, c + dc) === "#") continue
+      if (input[r + dr][c + dc] === "#") continue
       const newKey = `${r+dr},${c+dc},${newDir}`
       if (pqDict[newKey] !== undefined && pqDict[newKey].cost < cost) continue
       const newStep: Step = {
@@ -91,8 +90,71 @@ const part1 = (rawInput: string) => {
 
 const part2 = (rawInput: string) => {
   const input = parseInput(rawInput)
-
-  return
+  const startIndex = rawInput.indexOf('S')
+  const c0 = startIndex % (input[0].length + 1)
+  const r0 = (startIndex - c0) / (input[0].length + 1)
+  const pq = new Heap<Step>((a, b) => a.cost - b.cost)
+  pq.push({
+    r: r0,
+    c: c0,
+    dir: 0,
+    cost: 0,
+    prev: null
+  })
+  const pqDict: Record<string, Step> = {}
+  let bestCost = Number.POSITIVE_INFINITY
+  let visited = new Set<string>([`${r0},${c0}`])
+  while (pq.size() > 0) {
+    const prev = pq.pop()
+    const { r, c, dir, cost } = prev
+    const here = input[r][c]
+    if (here === 'E') {
+      if (cost > bestCost) break
+      bestCost = cost
+      let cursor = prev
+      visited.add(`${r},${c}`)
+      while (cursor.prev !== null) {
+        visited.add(`${cursor.r},${cursor.c}`)
+        cursor = cursor.prev
+      }
+      continue
+    }
+    for (let i = 0; i < (here === "S" ? 4 : 3); i += 1) {
+      const newDir = (dir + 3 + i) % 4 // left, ahead, right, u-turn
+      const [dr, dc] = deltas[newDir]
+      const addedCost = [1001, 1, 1001, 2001][i]
+      if (input[r + dr][c + dc] === "#") continue
+      const newKey = `${r+dr},${c+dc},${newDir}`
+      if (pqDict[newKey] !== undefined && pqDict[newKey].cost < cost) continue
+      const newStep: Step = {
+        r: r + dr,
+        c: c + dc,
+        dir: newDir,
+        cost: cost + addedCost,
+        prev,
+      }
+      pqDict[newKey] = newStep
+      pq.push(newStep)
+    }
+  }
+  { // draw it
+    console.log(
+      input
+        .map((row, r2) => {
+          return row
+            .map((cell, c2) => {
+              const key = `${r2},${c2}`
+              if (visited.has(key)) return bold("O")
+              if (cell === "#") return "\x1b[100m \x1b[0m"
+              if (cell === ".") return " "
+              return `\x1b[41m${cell}\x1b[0m`
+            })
+            .join("")
+        })
+        .join("\n"),
+    )
+  } // done drawing
+  return visited.size
 }
 
 run({