solve.js

#!/usr/bin/env node

require("lodash.combinations");
const { flatMap, combinations } = require("lodash");
const readline = require("readline");

const lines = [];

function processInput(lines) {
  const [firstLine, lastLine] = lines;

  const [max] = firstLine.split(" ");
  const pizzas = lastLine.split(" ");

  return {
    max: parseInt(max),
    pizzas: pizzas.map(number => parseInt(number))
  };
}

function transform({ max, pizzas }) {
  return flatMap(pizzas, (v, i, a) => combinations(a, i + 1))
    .reduce((currentSeq, seq) => {
      const partialTotal = seq.reduce((total, number) => total + number, 0);

      if (partialTotal < max) {
        return seq;
      }

      return currentSeq;
    })
    .map(number => pizzas.indexOf(number));
}

function processOutput(data) {
  console.log(data.length);
  console.log(data.join(" "));
}

readline
  .createInterface({
    input: process.stdin,
    output: process.stdout,
    terminal: false
  })
  .on("line", function(line) {
    lines.push(line);
  })
  .on("close", function() {
    processOutput(transform(processInput(lines)));
  });

cat input.txt | ./solve.js > output.txt

⚠️ solve.js must be executable:

chmod u+x ./solve.js