Three Sum

Problem Statement

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.

Here it the leetcode link to the problem 3Sum

Examples

Given array nums = [-1, 0, 1, 2, -1, -4],

A solution set is:
[
[-1, 0, 1],
[-1, -1, 2]
]

Solution

/**
* @param {number[]} nums
* @return {number[][]}
*/
var sortFunc = (a,b) => a-b;

var threeSum = function(nums) {
    const sum = 0;
    const len = nums.length;
    if(!nums || len < 3) return [];

    /** Sort the array first **/
    nums.sort(sortFunc);

    let arrayFinal = [];

    for(let i = 0; i< nums.length-2; i++){
        /** We start from both ends of the array **/
        let left = i+1;
        let right = nums.length-1;

        /** If same values, ignore and move to next **/
        if(i> 0 && nums[i] === nums[i-1]) continue;

        while(left < right){
            let cSum = nums[left] + nums[right] + nums[i]

            if(cSum < sum){
                /** Increment left **/
                left++;
            }else if(cSum > sum){
                /** decrease right **/
                right--;
            }else{
                let sumArr = [nums[left], nums[i], nums[right]].sort(sortFunc);
                arrayFinal.push(sumArr);
                /** Skip if values are similar**/
                while(nums[left] === nums[left+1]) left++;
                while(nums[right] === nums[right-1]) right--;
                left++;
                right--;
            }
        }

    }

    return arrayFinal;
};