Day 2

day2.peggy

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+lines = (@num|.., _| "\n")*
+
+num = n:$[0-9]+ { return parseInt(n, 10) }
+_ = [ \t]+

day2.ts

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+import { type MainArgs, parseFile } from './lib/utils.ts';
+
+type Parsed = number[][];
+
+function isSafe(levels: number[]): boolean {
+  if (levels.length < 2) {
+    return true;
+  }
+  let prev = levels[0];
+  const dir = Math.sign(prev - levels[1]);
+  for (let i = 1; i < levels.length; i++) {
+    const l = levels[i];
+    const diff = prev - l;
+    if ((diff === 0) || (Math.abs(diff) > 3) || (Math.sign(diff) !== dir)) {
+      return false;
+    }
+    prev = l;
+  }
+  return true;
+}
+
+function part1(inp: Parsed): number {
+  let count = 0;
+  for (const levels of inp) {
+    if (isSafe(levels)) {
+      count++;
+    }
+  }
+  return count;
+}
+
+function part2(inp: Parsed): number {
+  let count = 0;
+  for (const levels of inp) {
+    if (isSafe(levels)) {
+      count++;
+    } else {
+      for (let i=0; i < levels.length; i++) {
+        if (isSafe(levels.toSpliced(i, 1))) {
+          count++;
+          break;
+        }
+      }
+    }
+  }
+  return count;
+}
+
+export default async function main(args: MainArgs): Promise<[number, number]> {
+  const inp = await parseFile<Parsed>(args);
+  return [part1(inp), part2(inp)];
+}

test/day2.js

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+export default [326, 381];