aoc-2021/day01/day01.ts

import { reduce, tail, zip, map } from "fp-ts/lib/Array";
import { pipe } from "fp-ts/lib/function";
import { MonoidSum, Ord } from "fp-ts/lib/number";
import { getOrElse, chain } from "fp-ts/lib/Option";
import { lt } from "fp-ts/lib/Ord";
import { concatAll } from "fp-ts/lib/Monoid";

import { depthMeasurements } from "./input1";

const increaseCount = (as: number[]): number => pipe(
  zip(
    as,
    pipe(as, tail, getOrElse<number[]>(() => []))
  ),
  map(([a, b]) => lt(Ord)(a, b)),
  reduce(0, (acc, n) => n ? acc + 1 : acc)
);

const increases = pipe(
  depthMeasurements,
  increaseCount
);

console.log("number of times a depth measurement increases", increases);

const slidingWindows = (as: number[]): [number, number, number][] => pipe(
  zip(
    zip(
      as,
      pipe(as, tail, getOrElse<number[]>(() => []))
    ),
    pipe(as, tail, chain(tail), getOrElse<number[]>(() => [])),
  ),
  map(([[a, b], c]) => [a, b, c])
);

const slidingWindowSumsIncreases = pipe(
  depthMeasurements,
  slidingWindows,
  map(concatAll(MonoidSum)),
  increaseCount
);

console.log("number of times a 3 length sliding window measurement sum increases", slidingWindowSumsIncreases);