3sum.js

/**Given an integer array nums, return all the triplets [nums[i], nums[j], nums[k]] such that i != j, i != k, and j != k, and nums[i] + nums[j] + nums[k] == 0.

Notice that the solution set must not contain duplicate triplets. */

/**
 * @param {number[]} nums
 * @return {number[][]}
 */
 var threeSum = function(nums) {
    nums.sort((a, b) => a - b);
  
    let results = [];
  
    for (let i = 0; i < nums.length; i++) {
      let low = i + 1,
        high = nums.length,
        sum = 0;
  
      while (low < high) {
        sum = nums[i] + nums[low] + nums[high];
  
        if (sum === 0) {
          results.push([nums[i], nums[low], nums[high]]);
  
          while (nums[low + 1] === nums[low]) low++;
          while (nums[high - 1] === nums[high]) high--;
  
          low++;
          high--;
        } else if (sum < 0) {
          low++;
        } else {
          high--;
        }
      }
  
      while (nums[i + 1] === nums[i]) i++;
    }
  
    return results;
  };