From 3485e7ec80a54b8840bdd81f416af25f6637a744 Mon Sep 17 00:00:00 2001
From: Brad Adams <hi@breadadams.com>
Date: Thu, 19 Dec 2024 11:09:27 +0100
Subject: [PATCH] 19/2024

---
 2024/19/example.txt   | 10 ++++++
 2024/19/index.test.ts | 25 ++++++++++++++
 2024/19/index.ts      | 78 +++++++++++++++++++++++++++++++++++++++++++
 README.md             |  1 +
 4 files changed, 114 insertions(+)
 create mode 100644 2024/19/example.txt
 create mode 100644 2024/19/index.test.ts
 create mode 100644 2024/19/index.ts

diff --git a/2024/19/example.txt b/2024/19/example.txt
new file mode 100644
index 0000000..ad43a74
--- /dev/null
+++ b/2024/19/example.txt
@@ -0,0 +1,10 @@
+r, wr, b, g, bwu, rb, gb, br
+
+brwrr
+bggr
+gbbr
+rrbgbr
+ubwu
+bwurrg
+brgr
+bbrgwb
\ No newline at end of file
diff --git a/2024/19/index.test.ts b/2024/19/index.test.ts
new file mode 100644
index 0000000..5074e26
--- /dev/null
+++ b/2024/19/index.test.ts
@@ -0,0 +1,25 @@
+import { expect, describe, test } from "bun:test";
+import { part1, part2 } from ".";
+import { getInputs } from "../../utils/get-inputs";
+
+const { exampleInput, puzzleInput } = await getInputs("2024/19");
+
+describe("part 1", () => {
+  test("example", () => {
+    expect(part1(exampleInput)).toBe(6);
+  });
+
+  test("puzzle", () => {
+    expect(part1(puzzleInput)).toBe(358);
+  });
+});
+
+describe("part 2", () => {
+  test("example", () => {
+    expect(part2(exampleInput)).toBe(16);
+  });
+
+  test("puzzle", () => {
+    expect(part2(puzzleInput)).toBe(600639829400603);
+  });
+});
diff --git a/2024/19/index.ts b/2024/19/index.ts
new file mode 100644
index 0000000..c46037e
--- /dev/null
+++ b/2024/19/index.ts
@@ -0,0 +1,78 @@
+import { timePart1, timePart2 } from "../../utils/time-part";
+
+const parseInput = (input: string) => {
+  const [availableTowels, designs] = input.split("\n\n");
+
+  return {
+    availableTowels: availableTowels.split(", "),
+    designs: designs.split("\n"),
+  };
+};
+
+export const part1 = timePart1((input: string) => {
+  const { availableTowels, designs } = parseInput(input);
+  let possibleDesigns = 0;
+
+  for (const design of designs) {
+    let queue: Array<{ remaining: string }> = [];
+
+    for (const towel of availableTowels) {
+      if (design.indexOf(towel) === 0) {
+        queue.push({ remaining: design.substring(towel.length) });
+      }
+    }
+
+    while (queue.length) {
+      queue.sort((a, b) => a.remaining.length - b.remaining.length);
+      const entry = queue.shift()!;
+
+      for (const towel of availableTowels) {
+        if (entry.remaining.indexOf(towel) === 0) {
+          if (entry.remaining.length === towel.length) {
+            possibleDesigns++;
+            queue = [];
+            break;
+          }
+
+          queue.push({ remaining: entry.remaining.substring(towel.length) });
+        }
+      }
+    }
+  }
+
+  return possibleDesigns;
+});
+
+export const part2 = timePart2((input: string) => {
+  const { availableTowels, designs } = parseInput(input);
+  let possibleDesigns = 0;
+  const canBeCompleted = new Map<string, number>();
+
+  const countTowelVariants = (remaining: string) => {
+    if (canBeCompleted.has(remaining)) {
+      return canBeCompleted.get(remaining)!;
+    }
+
+    let variants = 0;
+
+    for (const towel of availableTowels) {
+      if (remaining.indexOf(towel) === 0) {
+        if (remaining.length === towel.length) {
+          variants++;
+          continue;
+        }
+
+        variants += countTowelVariants(remaining.substring(towel.length));
+      }
+    }
+
+    canBeCompleted.set(remaining, variants);
+    return variants;
+  };
+
+  for (const design of designs) {
+    possibleDesigns += countTowelVariants(design);
+  }
+
+  return possibleDesigns;
+});
diff --git a/README.md b/README.md
index d0e4de5..cbbc57c 100644
--- a/README.md
+++ b/README.md
@@ -6,6 +6,7 @@
 
 |                    Day                     | Part 1 | Part 2 |
 | :----------------------------------------: | :----: | :----: |
+| [19](https://adventofcode.com/2024/day/19) |   ✅   |   ✅   |
 | [18](https://adventofcode.com/2024/day/18) |   ✅   |   ✅   |
 | [17](https://adventofcode.com/2024/day/17) |   ✅   |   ✅   |
 | [16](https://adventofcode.com/2024/day/16) |   ✅   |   ✅   |