3Sum JavaScript

index.js

/**
 * @param {number[]} nums
 * @return {number[][]}
 */
var threeSum = function(nums) {
    nums.sort((a, b) => { return a - b; });
    const result = [];
    for (let i = 0; i < (nums.length-2); i ++) {
        const a = nums[i];
        if (a > 0) return result; // all other numbers to the right are positive as we are working with sorted array
        if (i > 0 && a === nums[i - 1]) continue;
        
        let start = i + 1;
        let end = nums.length - 1;
        
        while (start < end) {
            const b = nums[start];
            const c = nums[end];
            if (a + b + c === 0) {
                result.push([a,b,c]);
                while (nums[end - 1] === c) { end--; }
                while (nums[start + 1] === b) { start++; }
                end--;
                start++;
            } else if (a + b + c > 0) {
                end--;
            } else {
                start++;
            }
        }
    }
    return result;
};