From be9e7619cdf2235be42b86fba0c59f07b8e26f04 Mon Sep 17 00:00:00 2001
From: David Ashby <delta.mu.alpha@gmail.com>
Date: Tue, 17 Dec 2024 20:50:33 -0500
Subject: [PATCH] day 13 has some issues

---
 13/index.ts | 79 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)
 create mode 100644 13/index.ts

diff --git a/13/index.ts b/13/index.ts
new file mode 100644
index 0000000..c991d87
--- /dev/null
+++ b/13/index.ts
@@ -0,0 +1,79 @@
+import fs from "node:fs";
+import { printTime, now, toNum } from "../util";
+
+const test = false;
+
+type coord = { x: bigint; y: bigint };
+
+const data = fs.readFileSync(
+  test ? "./inputs/testinput" : "./inputs/input",
+  "utf8"
+);
+
+let timer = now.instant();
+console.log(
+  "part one:",
+  data
+    .split("\n")
+    .slice(0, -1)
+    .reduce((machines, curr, index) => {
+      // parse this mess
+      const machine = Math.floor(index / 4);
+      switch (index % 4) {
+        case 0:
+          machines[machine] = {
+            ...machines[machine],
+            A: { x: BigInt(curr.slice(11, 14)), y: BigInt(curr.slice(17)) },
+          };
+          break;
+        case 1:
+          machines[machine] = {
+            ...machines[machine],
+            B: { x: BigInt(curr.slice(11, 14)), y: BigInt(curr.slice(17)) },
+          };
+          break;
+        case 2:
+          let coords = curr.slice(9).split(", ");
+          machines[machine] = {
+            ...machines[machine],
+            Prize: { x: BigInt(coords[0]), y: BigInt(coords[1].slice(2)) },
+          };
+        // skip processing the blank line
+      }
+      return machines;
+    }, [] as Array<{ A: coord; B: coord; Prize: coord }>)
+    .filter((machine) => {
+      // remove machines where it's impossible to reach the prize within 100 presses of each button
+      return !(
+        machine.A.x * BigInt(100) + machine.B.x * BigInt(100) <
+          machine.Prize.x ||
+        machine.A.y * BigInt(100) + machine.B.y * BigInt(100) < machine.Prize.y
+      );
+    })
+    .map((m) => {
+      //94a/22 - 34a/67 = 8400/22 - 5400/67
+      for (let a = BigInt(0); a < 101; a++) {
+        if (
+          (m.A.x * a) / m.B.x - (m.A.y * a) / m.B.y ==
+          m.Prize.x / m.B.x - m.Prize.y / m.B.y
+        ) {
+          // b = 8400/22 - 94(a)/22
+          return a * BigInt(3) + m.Prize.x / m.B.x - (m.A.x * a) / m.B.x;
+        }
+      }
+    })
+    .reduce((total: bigint, m) => {
+      if (m !== undefined) {
+        return total + m;
+      }
+      return total;
+    }, BigInt(0)),
+  printTime(now.instant().since(timer))
+);
+
+// timer = now.instant();
+// console.log(
+//   "part two:",
+//   data.split("\n").slice(0, -1),
+//   printTime(now.instant().since(timer))
+// );