export function groupConsecutiveDuplicates(nums: number[]): number[][] {
  let result: number[][] = [];

  for (const val of nums) {
    let last = result[result.length - 1];
    if (last && last[0] === val) {
      last.push(val);
    } else {
      result.push([val]);
    }
  }

  return result;
}