day 02 (#9)

.vscode/days.code-snippets

@@ -14,8 +14,8 @@
             "}",
             "",
             "if (import.meta.main) {",
-            "  console.log(part1(loadInput($1)));",
-            "  console.log(part2(loadInput($1)));",
+            "  console.log(part1(await loadInput($1)));",
+            "  console.log(part2(await loadInput($1)));",
             "}"
         ],
 		"description": "implementation for daily challenge"

days/02/main.ts

@@ -0,0 +1,38 @@
+import { loadInput } from "utils";
+
+export function part1(input: Array<string>) {
+  const reports = parseReports(input);
+  const safeReports = reports.filter(isReportSafe);
+  return safeReports.length;
+}
+
+export function part2(input: Array<string>) {
+  const reports = parseReports(input);
+  const safeReports = reports.filter((r) =>
+    isReportSafe(r) || isDampenedReportSafe(r)
+  );
+  return safeReports.length;
+}
+
+function parseReports(input: Array<string>) {
+  return input.map((l) => l.split(" ").map(Number));
+}
+
+function isReportSafe(report: Array<number>) {
+  if (report.length < 2) return true;
+  const direction = report[0] - report[1] > 0 ? -1 : 1;
+  for (let i = 1; i < report.length; i += 1) {
+    const diff = (report[i - 1] - report[i]) * -direction;
+    if (diff < 1 || diff > 3) return false;
+  }
+  return true;
+}
+
+function isDampenedReportSafe(report: Array<number>) {
+  return report.map((_, i) => report.toSpliced(i, 1)).some(isReportSafe);
+}
+
+if (import.meta.main) {
+  console.log(part1(await loadInput(2)));
+  console.log(part2(await loadInput(2)));
+}

days/02/main_test.ts

@@ -0,0 +1,19 @@
+import { expect } from "@std/expect";
+import { part1, part2 } from "./main.ts";
+
+const input = [
+  "7 6 4 2 1",
+  "1 2 7 8 9",
+  "9 7 6 2 1",
+  "1 3 2 4 5",
+  "8 6 4 4 1",
+  "1 3 6 7 9",
+];
+
+Deno.test("part 1", () => {
+  expect(part1(input)).toBe(2);
+});
+
+Deno.test("part 2", () => {
+  expect(part2(input)).toBe(4);
+});

days/mod.ts

@@ -3,7 +3,7 @@ type Solution = { part1: PartFunction; part2: PartFunction };
 
 const days: Record<string, Solution> = {};
 
-for (const day of [1]) {
+for (const day of [1, 2]) {
   days[pad(day)] = await import(`./${pad(day)}/main.ts`);
 }