function dominator(a: number[]): number {
  let size = 0;
  let value = 0;
  let index = 0;

  a.forEach((v, k) => {
    if (size === 0) {
      size++;
      value = v;
      index = k;
    } else if (value !== v) {
      size--;
    } else {
      size++;
    }
  });

  const candidate = size > 0 ? value : -1;

  let count = 0;
  for (const v of a) {
    if (v === candidate) {
      count++;
    }
  }

  if (count <= a.length / 2) {
    index = -1;
  }

  return index;
}