index.ts

export const fourSum = (nums: number[], target: number) => {
  nums.sort((x, y) => x - y)
  let res = []

  for (let i = 0; i < nums.length - 3; i++) {
    if (i > 0 && nums[i - 1] === nums[i]) continue
    for (let j = i + 1; j < nums.length - 2; j++) {
      if (j > i + 1 && nums[j - 1] === nums[j]) continue
      let l = j + 1
      let r = nums.length - 1

      while (l < r) {
        const sum = nums[i] + nums[j] + nums[l] + nums[r]
        if (sum === target) {
          res.push([nums[i], nums[j], nums[l], nums[r]])
          l++
          r--
          while (l < r && nums[l] === nums[l - 1]) l++
          while (l < r && nums[r] === nums[r + 1]) r--
        } else if (sum < target) {
          l++
        } else {
          r--
        }
      }
    }
  }

  return res
}