Day 2: Red-Nosed Reports

Megathread guidelines

  • Keep top level comments as only solutions, if you want to say something other than a solution put it in a new post. (replies to comments can be whatever)
  • You can send code in code blocks by using three backticks, the code, and then three backticks or use something such as https://blocks.programming.dev if you prefer sending it through a URL

FAQ

  • @[email protected]
    2•7 months ago

    JavaScript

    Also wrote a solution in JavaScript to play around with list comprehension. Wrote some utility functions for expressiveness (and lazy evaluation).

    Code 
    const fs = require("fs");
const U = require("./util");

const isSafe = xs =>
    U.pairwise(xs).every(([a,b]) => a!==b && a-b > -4 && a-b < 4) &&
    new Set(U.pairwise(xs).map(([a,b]) => a < b)).size === 1;

const rows = fs
    .readFileSync(process.argv[2] || process.stdin.fd, "utf8")
    .split("\n")
    .filter(x => x != "")
    .map(x => x.split(/ +/).map(Number));

const p1 = U.countBy(rows, isSafe);
const p2 = U.countBy(rows, row =>
    isSafe(row) || U.someBy(U.indices(row),
        i => isSafe([...row.slice(0, i), ...row.slice(i+1)])));

console.log("02:", p1, p2);

    https://github.com/sjmulder/aoc/blob/master/2024/js/day02.js