From 63261538ec22d5a65d486a2b037dc10005220134 Mon Sep 17 00:00:00 2001
From: Zynh Ludwig <zynh0722@gmail.com>
Date: Wed, 4 Dec 2024 22:08:04 -0800
Subject: [PATCH] ugg :(

---
 .gitignore     |  3 +++
 day4/part2.lua |  6 ++----
 day4/part2.ts  | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 54 insertions(+), 4 deletions(-)
 create mode 100644 .gitignore
 create mode 100644 day4/part2.ts

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..e8625c1
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+package.json
+package-lock.json
+node_modules
diff --git a/day4/part2.lua b/day4/part2.lua
index 2e88e07..87d2ae3 100644
--- a/day4/part2.lua
+++ b/day4/part2.lua
@@ -28,8 +28,6 @@ local lines = lines_from(file)
 
 ---@diagnostic disable-next-line: redefined-local
 local function count_xmas_at_index(lines, line_idx, char_idx)
-	local line = lines[line_idx]
-
 	local up_idx = line_idx - 1
 	local down_idx = line_idx + 1
 	local right_idx = char_idx + 1
@@ -39,7 +37,7 @@ local function count_xmas_at_index(lines, line_idx, char_idx)
 	char_count["M"] = 0
 	char_count["S"] = 0
 	if up_idx >= 1 then
-		if right_idx <= #line then
+		if right_idx <= #lines[up_idx] then
 			local key = lines[up_idx]:sub(right_idx, right_idx)
 			if char_count[key] ~= nil then
 				char_count[key] = char_count[key] + 1
@@ -55,7 +53,7 @@ local function count_xmas_at_index(lines, line_idx, char_idx)
 	end
 
 	if down_idx <= #lines then
-		if right_idx <= #line then
+		if right_idx <= #lines[down_idx] then
 			local key = lines[down_idx]:sub(right_idx, right_idx)
 			if char_count[key] ~= nil then
 				char_count[key] = char_count[key] + 1
diff --git a/day4/part2.ts b/day4/part2.ts
new file mode 100644
index 0000000..bf2ec70
--- /dev/null
+++ b/day4/part2.ts
@@ -0,0 +1,49 @@
+const inputFile = await Bun.file("input").text();
+
+const lines = inputFile.split("\n").filter((x) => x);
+
+function between(x: number, min: number, max: number): boolean {
+  return x >= min && x < max;
+}
+
+function countMs(str: string) {
+  return (str.match(/M/g) || []).length;
+}
+
+function countSs(str: string) {
+  return (str.match(/S/g) || []).length;
+}
+
+let xmasCount = 0;
+
+for (let lineIdx = 0; lineIdx < lines.length; lineIdx++) {
+  for (let charIdx of lines[lineIdx]
+    .matchAll(/A/g)
+    .toArray()
+    .map((m) => m.index)) {
+    let charPositions = [
+      [lineIdx - 1, charIdx - 1], // up left
+      [lineIdx - 1, charIdx + 1], // up right
+      [lineIdx + 1, charIdx - 1], // down left
+      [lineIdx + 1, charIdx + 1], // down right
+    ].filter(
+      ([li, ci]) =>
+        between(li, 0, lines.length) && between(ci, 0, lines[lineIdx].length),
+    );
+
+    if (charPositions.length === 4) {
+      let corners = "";
+      for (let [li, ci] of charPositions) {
+        corners += lines[li][ci];
+      }
+
+      if (countMs(corners) == 2 && countSs(corners) == 2) {
+        xmasCount += 1;
+      }
+    }
+  }
+}
+
+console.log(xmasCount);
+
+export {};