fourSum.js

/**
Given an array nums of n integers, return an array of all the unique quadruplets [nums[a], nums[b], nums[c], nums[d]] such that:

0 <= a, b, c, d < n
a, b, c, and d are distinct.
nums[a] + nums[b] + nums[c] + nums[d] == target
You may return the answer in any order.

Example 1:
Input: nums = [1,0,-1,0,-2,2], target = 0
Output: [[-2,-1,1,2],[-2,0,0,2],[-1,0,0,1]]

Example 2:
Input: nums = [2,2,2,2,2], target = 8
Output: [[2,2,2,2]]

* @param {number[]} nums
* @param {number} target
* @return {number[][]}
*/
var fourSum = function (nums, target) {
  const log = [];
  nums.sort((a, b) => a - b);

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

      let l = j + 1;
      let r = nums.length - 1;

      while (l < r) {
        let sum = nums[i] + nums[j] + nums[l] + nums[r];

        if (sum === target) {
          log.push([nums[i], nums[j], nums[l], nums[r]]);

          while (l < r && nums[l] === nums[l + 1]) l++;
          while (l < r && nums[r] === nums[r - 1]) r--;

          l++;
          r--;
        } else if (sum < target) l++;
        else r--;
      }
    }
  }

  return log;
};