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Find all unique triplets in the array which gives the sum of zero

Leetcode Problem 15 — 3Sum

Difficulty: Medium
Given an array nums of n integers, are there elements a, b, c in nums such that a + b + c= 0? Find all unique triplets in the array which gives the sum of zero.
Note:
The solution set must not contain duplicate triplets.
Example:
Given array nums = [-1, 0, 1, 2, -1, -4]

Solution in javascript with explanation of the logic in plain english below:

const threeSum = (nums, target) => {
  const hash = {};
  const ans = [];
  for (let i = 0; i < nums.length; i++) {
    for (key in hash) {
      if(hash[key][target - (nums[i] + +key)] === undefined) {
        hash[key][nums[i]] = null;
      } else {
        hash[key][target - (nums[i] + +key)] = nums[i];
        ans.push([+key, target - (nums[i] + +key), nums[i]]);
      }
    }
    if (hash[nums[i]] === undefined) {
      hash[nums[i]] = {}
    }
  }
  return ans;
}

Example

console.log(threeSum([-1, 0, 1, 2, -1, -4], 0));

Output

[ [ -1, 0, 1 ], [ 0, 1, -1 ], [ -1, 2, -1 ] ]

Explanation

{
    -1: {0:1, 1:null, 2:-1, -1:null, -4:null},
    0: {1:-1, 2: null, -1:null, -4:null},
    1: {2: null, -1:null, -4: null},
    2: {-1:null, -4:null},
    -4: {}
}
  1. iterate through array > if not in object, add to object
  2. iterate through objects > if not in object of object, add it with value as null | else log

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