Ba Tổng Bằng Không3Sum

function threeSum(nums: number[]): number[][] {
  const result: number[][] = []
  const seen = new Set<string>()
  for (let i = 0; i < nums.length - 2; i++) {
    for (let j = i + 1; j < nums.length - 1; j++) {
      for (let k = j + 1; k < nums.length; k++) {
        if (nums[i] + nums[j] + nums[k] === 0) {
          const triple = [nums[i], nums[j], nums[k]].sort((a, b) => a - b)
          const key = triple.join(',')
          if (!seen.has(key)) { seen.add(key); result.push(triple) }
        }
      }
    }
  }
  return result
}