balance.js

import _ from "lodash";
import fs from "fs";

const compareOccurrences = (occurrences) => {
  let differences = 0;
  for (let key of Object.keys(occurrences)) {
    if (occurrences[key] !== 0) differences++;
    if (differences > 1) return false;
  }
  if (differences === 1) return true;
  return false;
};

const test = (str, minus = 1) => {
  const left = str.slice(0, str.length / 2 + minus).split("");
  const right = str.slice(str.length / 2 + minus).split("");
  const occurrences = {};
  for (let j = 0; j < left.length; j++) {
    occurrences[left[j]] ? occurrences[left[j]]-- : (occurrences[left[j]] = -1);
  }
  for (let j = 0; j < right.length; j++) {
    occurrences[right[j]]
      ? occurrences[right[j]]++
      : (occurrences[right[j]] = 1);
    if (occurrences[right[j]] > 1) return false;
  }

  return compareOccurrences(occurrences);
};

const isAlmostBalance = (str) => {
  if (str.length % 2 == 0) return false;
  return test(str, 0) || test(str, 1);
};

const data = fs
  .readFileSync("perfectly_balanced_chapter_1_input.txt")
  .toString()
  .split("\n");
let nbWords = parseInt(data[0]);
let cursor = 1;

for (let iWord = 0; iWord < nbWords; iWord++) {
  const word = data[cursor++];
  const nbChecks = data[cursor++];
  let nbTrue = 0;
  for (let j = 0; j < nbChecks; j++) {
    const [start, end] = data[cursor++].split(" ");

    const subWord = word.slice(start - 1, end);
    if (isAlmostBalance(subWord)) {
      nbTrue++;
    }
  }

  console.log(`Case #${iWord + 1}: ${nbTrue}`);
}