From 5764869e99ade916d2a7c98af7d5953fdae86d99 Mon Sep 17 00:00:00 2001
From: Joshua Seigler <joshua@seigler.net>
Date: Wed, 4 Dec 2024 23:05:28 -0500
Subject: [PATCH] much cleaner way to look for shapes in grids

---
 .aocrunner.json    |   6 +--
 src/day04/index.ts | 126 +++++++++------------------------------------
 2 files changed, 28 insertions(+), 104 deletions(-)

diff --git a/.aocrunner.json b/.aocrunner.json
index eeaeccf..9b9c941 100644
--- a/.aocrunner.json
+++ b/.aocrunner.json
@@ -48,17 +48,17 @@
     {
       "part1": {
         "solved": true,
-        "result": "2358",
+        "result": "2143",
         "attempts": [
           "0"
         ],
-        "time": 327.70272
+        "time": 67.709144
       },
       "part2": {
         "solved": true,
         "result": "1737",
         "attempts": [],
-        "time": 201.22507
+        "time": 182.986319
       }
     },
     {
diff --git a/src/day04/index.ts b/src/day04/index.ts
index 872ca5c..0d9bdf4 100644
--- a/src/day04/index.ts
+++ b/src/day04/index.ts
@@ -4,118 +4,42 @@ const parseInput = (rawInput: string) => {
   return rawInput.split('\n').map(line => line.split(''))
 }
 
-const directions = ["down","right","dl","dr"] as const
-type Direction = typeof directions[number]
-type Prospect1 = {
-  letters: string
-  direction: Direction
-  next: [number, number]
-}
-type Coord = Prospect1['next']
-const getNext = (dir: Direction, [row, col]: Coord): Coord => {
-  switch(dir) {
-    case "down": {return [row+1, col]}
-    case "right": {return [row, col+1]}
-    case "dl": {return [row+1, col-1]}
-    case "dr": {return [row+1, col+1]}
-  }
-}
-
 const part1 = (rawInput: string) => {
   const input = parseInput(rawInput)
   let total = 0
-  let prospects: Prospect1[] = []
-  input.forEach((line, row) => {
-    line.forEach((letter, col) => {
-      prospects = prospects.map((prospect) => {
-        const {
-          direction,
-          letters,
-          next
-        } = prospect
-        if (next[0] < row) return null
-        if (next[0] === row && next[1] === col) {
-          const nextLetters = letters + letter
-          if (["XMAS","SAMX"].includes(nextLetters)) {
-            total += 1
-            return null
-          }
-          if (["XMA","SAM","XM","SA"].includes(nextLetters)) {
-            return {
-              letters: nextLetters,
-              direction: direction,
-              next: getNext(direction, next)
-            }
-          }
-        }
-        return prospect
-      }).filter(prospect => prospect != null)
-      if ("XMAS".includes(letter)) {
-        directions.forEach(direction => {
-          prospects.push({
-            letters: letter,
-            direction,
-            next: getNext(direction, [row, col])
-          })
-        })
-      }
+  input.forEach((line,r) => {
+    line.forEach((cell, c) => {
+      total += [
+        [[r,c],[r,c+1],[r,c+2],[r,c+3]], // right
+        [[r,c],[r+1,c+1],[r+2,c+2],[r+3,c+3]], // downright
+        [[r,c],[r+1,c],[r+2,c],[r+3,c]], // down
+        [[r,c],[r+1,c-1],[r+2,c-2],[r+3,c-3]], // downleft
+      ].reduce((acc,cur) => /XMAS|SAMX/.test(cur.map(([r,c]) => {
+        return (input[r] ?? [])[c] ?? "."
+      }).join('')) ? acc+1:acc, 0)
     })
   })
   return total
 }
 
-type Prospect2 = {
-  letters: string
-  direction: Direction
-  next: [number, number]
-  center: [number, number]
-}
-
 const part2 = (rawInput: string) => {
   const input = parseInput(rawInput)
-  let centers = new Map<string, number>()
-  let prospects: Prospect2[] = []
   let total = 0
-  input.forEach((line, row) => {
-    line.forEach((letter, col) => {
-      prospects = prospects.map((prospect) => {
-        const {
-          direction,
-          letters,
-          next
-        } = prospect
-        if (next[0] < row) return null
-        if (next[0] === row && next[1] === col) {
-          const nextLetters = letters + letter
-          if (["MAS","SAM"].includes(nextLetters)) {
-            const key = prospect.center.join(",")
-            if (centers.has(key)) { total++ }
-            centers.set(key, 1)
-            return null
-          }
-          if (["MA","SA"].includes(nextLetters)) {
-            return {
-              ...prospect,
-              letters: nextLetters,
-              next: getNext(direction, next),
-            }
-          }
-        }
-        return prospect
-      }).filter(prospect => prospect != null)
-      if ("XMAS".includes(letter)) {
-        ["dl" as const, "dr" as const].forEach(direction => {
-          const center = getNext(direction, [row, col])
-          prospects.push({
-            letters: letter,
-            direction,
-            next: center,
-            center,
-          })
-        })
+  for (let r = 0; r < input.length -2; r++) {
+    for (let c = 0; c < input[0].length -2; c++) {
+      if(/MMASS|SSAMM|MSAMS|SMASM/.test(
+        [
+          [r,c],
+          [r,c+2],
+          [r+1,c+1],
+          [r+2,c],
+          [r+2,c+2]
+        ].map(([r,c]) => input[r][c]).join('')
+      )) {
+        total++
       }
-    })
-  })
+    }
+  }
   return total
 }
 
@@ -165,5 +89,5 @@ MXMXAXMASX`,
     solution: part2,
   },
   trimTestInputs: true,
-  onlyTests: false,
+  onlyTests: true,
 })