freeCodeCamp Challenge Guide: Problem 32: Pandigital products

Guide
1

Problem 32: Pandigital products

Solutions

Solution 1 (Click to Show/Hide) 
function pandigitalProducts(n) {
  function is1toNPandigital(n, digitStr) {
    // check if length is n
    if (digitStr.length !== n) {
      return false;
    }
    // check if pandigital
    for (let i = digitStr.length; i > 0; i--) {
      if (digitStr.indexOf(i.toString()) === -1) {
        return false;
      }
    }
    return true;
  }
  function concatenateNums(...numbers) {
    let digitStr = '';
    for (let i = 0; i < numbers.length; i++) {
      digitStr += numbers[i].toString();
    }
    return digitStr;
  }

  const pandigitalNums = [];
  const limit = 10 ** Math.floor(n / 2) - 1;
  let sum = 0;
  for (let mult1 = 2; mult1 < limit; mult1++) {
    for (let mult2 = 2; mult2 < limit; mult2++) {
      const product = mult1 * mult2;
      const concatenated = concatenateNums(mult1, mult2, product);
      if (concatenated.length > n) {
        break;
      } else if (concatenated.length < n) {
        continue;
      }
      if (
        is1toNPandigital(n, concatenated) &&
        !pandigitalNums.includes(product)
      ) {
        pandigitalNums.push(product);
        sum += product;
      }
    }
  }
  return sum;
}
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