Sum of the 3 Zero

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.

The solution set must not contain duplicate triplets.

Example:

Input: nums = [-1, 0, 1, 2, -1, -4]
Output:
[
  [-1, 0, 1],
  [-1, -1, 2]
]

Solution

/**
 * @param {number[]} nums
 * @return {number[][]}
 */
var threeSum = function (nums) {
    var len = nums.length;
    var res = [];
    var l = 0;
    var r = 0;
    nums.sort((a, b) => a - b);
    for (var i = 0; i < len; i++) {
        if (i > 0 && nums[i] === nums[i - 1]) continue;
        l = i + 1;
        r = len - 1;
        while (l < r) {
            if (nums[i] + nums[l] + nums[r] < 0) {
                l++;
            } else if (nums[i] + nums[l] + nums[r] > 0) {
                r--;
            } else {
                res.push([nums[i], nums[l], nums[r]]);
                while (l < r && nums[l] === nums[l + 1]) l++;
                while (l < r && nums[r] === nums[r - 1]) r--;
                l++;
                r--;
            }
        }
    }
    return res;
};

Complexity:

• Time complexity: O(n^2).
• Space complexity: O(1).