3Sum

Description

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

Solution(javascript)

/**
 * @param {number[]} nums
 * @return {number[][]}
 */
var threeSum = function(nums) {
    var rtn = [];
    if (nums.length < 3) {
        return rtn;
    }
    nums = nums.sort(function(a, b) {
        return a - b;
    });
    for (var i = 0; i < nums.length - 2; i++) {
        if (nums[i] > 0) {
            return rtn;
        }
        if (i > 0 && nums[i] == nums[i - 1]) {
            continue;
        }
        for (var j = i + 1, k = nums.length - 1; j < k;) {
            if (nums[i] + nums[j] + nums[k] === 0) {
                rtn.push([nums[i], nums[j], nums[k]]);
                j++;
                k--;
                while (j < k && nums[j] == nums[j - 1]) {
                    j++;
                }
                while (j < k && nums[k] == nums[k + 1]) {
                    k--;
                }
            } else if (nums[i] + nums[j] + nums[k] > 0) {
                k--;
            } else {
                j++;
            }
        }
    }
    return rtn;
};