Leetcode [Hard] 1363. Largest Multiple of Three

leetcode-1363. Largest Multiple of Three.ts

function largestMultipleOfThree(digits: number[]): string {
  // Digits sorted in ascending order
  const digitsAsc = [...digits].sort((a, b) => a - b);
  // Sorting the digits in descending order 9,8,7...
  const digitsDesc = [...digits].sort((a, b) => b - a); // [8,7,6,1,0]

  let sum = digits.reduce((prev, curr) => prev + curr, 0);

  let remainder = sum % 3;
  let result = digitsDesc;

  if (remainder === 0 && sum !== 0) return digitsDesc.join("");

  const REMAINDER_OF_1 = [1, 4, 7];
  const REMAINDER_OF_2 = [2, 5, 8];

  let indexToRemove: number;

  function handleRemovalIfResultContains(arr: number[]) {
    for (const d of arr) {
      if (result.includes(d)) {
        indexToRemove = result.indexOf(d);
        sum -= d;
        break;
      }
    }
  }

  const NUMS_REMAINDER_IS_1 = [2, 4, 7];
  const NUMS_REMAINDER_IS_2 = [1, 5, 8];

  for (let i = 0; i < digits.length; i++) {
    const digit = digitsAsc[i];

    if (digit === 0) continue;
    else if (remainder === 0) break;


    if (result.includes(remainder)) {
      indexToRemove = result.indexOf(remainder);
      remainder = 0;
    } else {
      if (remainder === 1) {
        handleRemovalIfResultContains(NUMS_REMAINDER_IS_1);

        if (indexToRemove === undefined) {
          handleRemovalIfResultContains(NUMS_REMAINDER_IS_2);
        }
      } else if (remainder === 2) {
        handleRemovalIfResultContains(NUMS_REMAINDER_IS_2);

        if (indexToRemove === undefined) {
          handleRemovalIfResultContains(NUMS_REMAINDER_IS_1);
        }
      }

      // Where we would get rid of the 8
      remainder = sum % 3;
    }

    result.splice(indexToRemove, 1);
  }

  const strResult = remainder === 0 ? result.join("") : "";

  return strResult.replace(/^0+(?=\d)/, "");
}