3Sum — LeetCode #15

Given an integer array nums, return all the triplets [nums[i], nums[j], nums[k]] such that i != j, i != k, and j != k, and nums[i] + nums[j] + nums[k] == 0.

Notice that the solution set must not contain duplicate triplets.

Example 1:

Input: nums = [-1,0,1,2,-1,-4]
Output: [[-1,-1,2],[-1,0,1]]
Explanation: 
nums[0] + nums[1] + nums[2] = (-1) + 0 + 1 = 0.
nums[1] + nums[2] + nums[4] = 0 + 1 + (-1) = 0.
nums[0] + nums[3] + nums[4] = (-1) + 2 + (-1) = 0.
The distinct triplets are [-1,0,1] and [-1,-1,2].
Notice that the order of the output and the order of the triplets does not matter.

Example 2:

Input: nums = [0,1,1]
Output: []
Explanation: The only possible triplet does not sum up to 0.

Example 3:

Input: nums = [0,0,0]
Output: [[0,0,0]]
Explanation: The only possible triplet sums up to 0.

Constraints:

• 3 <= nums.length <= 3000
• -105 <= nums[i] <= 105

Solutions:

Python

class Solution:
    def threeSum(self, nums: List[int]) -> List[List[int]]:
        nums.sort()
        result = []
        for i in range(len(nums) - 2):
            if i > 0 and nums[i] == nums[i - 1]:
                continue
            left, right = i + 1, len(nums) - 1
            while left < right:
                total = nums[i] + nums[left] + nums[right]
                if total == 0:
                    result.append([nums[i], nums[left], nums[right]])
                    while left < right and nums[left] == nums[left + 1]:
                        left += 1
                    while left < right and nums[right] == nums[right - 1]:
                        right -= 1
                    left += 1
                    right -= 1
                elif total < 0:
                    left += 1
                else:
                    right -= 1
        return result

C#

public class Solution {
    public IList<IList<int>> ThreeSum(int[] nums) {
        Array.Sort(nums);
        var result = new List<IList<int>>();
        for (int i = 0; i < nums.Length - 2; i++)
        {
            if (i > 0 && nums[i] == nums[i - 1])
            {
                continue;
            }
            int left = i + 1, right = nums.Length - 1;
            while (left < right)
            {
                int total = nums[i] + nums[left] + nums[right];
                if (total == 0)
                {
                    result.Add(new List<int> { nums[i], nums[left], nums[right] });
                    while (left < right && nums[left] == nums[left + 1])
                    {
                        left++;
                    }
                    while (left < right && nums[right] == nums[right - 1])
                    {
                        right--;
                    }
                    left++;
                    right--;
                }
                else if (total < 0)
                {
                    left++;
                }
                else
                {
                    right--;
                }
            }
        }
        return result;
    }
}

Java

class Solution {
    public List<List<Integer>> threeSum(int[] nums) {
        Arrays.sort(nums);
        var result = new ArrayList<List<Integer>>();
        for (int i = 0; i < nums.length - 2; i++)
        {
            if (i > 0 && nums[i] == nums[i - 1])
            {
                continue;
            }
            int left = i + 1, right = nums.length - 1;
            while (left < right)
            {
                int total = nums[i] + nums[left] + nums[right];
                if (total == 0)
                {
                    result.add(Arrays.asList(nums[i], nums[left], nums[right]));
                    while (left < right && nums[left] == nums[left + 1])
                    {
                        left++;
                    }
                    while (left < right && nums[right] == nums[right - 1])
                    {
                        right--;
                    }
                    left++;
                    right--;
                }
                else if (total < 0)
                {
                    left++;
                }
                else
                {
                    right--;
                }
            }
        }
        return result;
    }
}

Javascript

/**
 * @param {number[]} nums
 * @return {number[][]}
 */
var threeSum = function(nums) {
    nums.sort((a, b) => a - b);
    const result = [];
    for (let i = 0; i < nums.length - 2; i++) {
        if (i > 0 && nums[i] === nums[i - 1]) {
            continue;
        }
        let left = i + 1, right = nums.length - 1;
        while (left < right) {
            const total = nums[i] + nums[left] + nums[right];
            if (total === 0) {
                result.push([nums[i], nums[left], nums[right]]);
                while (left < right && nums[left] === nums[left + 1]) {
                    left++;
                }
                while (left < right && nums[right] === nums[right - 1]) {
                    right--;
                }
                left++;
                right--;
            } else if (total < 0) {
                left++;
            } else {
                right--;
            }
        }
    }
    return result;
};

Typescript

function threeSum(nums: number[]): number[][] {
    nums.sort((a, b) => a - b);
    const result: number[][] = [];
    for (let i = 0; i < nums.length - 2; i++) {
        if (i > 0 && nums[i] === nums[i - 1]) {
            continue;
        }
        let left = i + 1, right = nums.length - 1;
        while (left < right) {
            const total = nums[i] + nums[left] + nums[right];
            if (total === 0) {
                result.push([nums[i], nums[left], nums[right]]);
                while (left < right && nums[left] === nums[left + 1]) {
                    left++;
                }
                while (left < right && nums[right] === nums[right - 1]) {
                    right--;
                }
                left++;
                right--;
            } else if (total < 0) {
                left++;
            } else {
                right--;
            }
        }
    }
    return result;
};

PHP

class Solution {

    /**
     * @param Integer[] $nums
     * @return Integer[][]
     */
    function threeSum($nums) {
        sort($nums);
        $result = [];
        for ($i = 0; $i < count($nums) - 2; $i++) {
            if ($i > 0 && $nums[$i] == $nums[$i - 1]) {
                continue;
            }
            $left = $i + 1;
            $right = count($nums) - 1;
            while ($left < $right) {
                $total = $nums[$i] + $nums[$left] + $nums[$right];
                if ($total == 0) {
                    $result[] = [$nums[$i], $nums[$left], $nums[$right]];
                    while ($left < $right && $nums[$left] == $nums[$left + 1]) {
                        $left++;
                    }
                    while ($left < $right && $nums[$right] == $nums[$right - 1]) {
                        $right--;
                    }
                    $left++;
                    $right--;
                } else if ($total < 0) {
                    $left++;
                } else {
                    $right--;
                }
            }
        }
        return $result;
    }
}

I hope this helps! Let me know if you have any questions. Don’t forget to follow and give some claps and comments