# 15. 3Sum

## Medium

***

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]]
```

**Example 2:**

```
Input: nums = []
Output: []
```

**Example 3:**

```
Input: nums = [0]
Output: []
```

**Constraints:**

* `0 <= nums.length <= 3000`
* `-105 <= nums[i] <= 105`

**Solution**

```python
class Solution:
    def threeSum(self, nums: List[int]) -> List[List[int]]:
        nums = sorted(nums)
        length = len(nums)
        result = []
        for index, value in enumerate(nums):
            if index > 0 and nums[index-1] == value:
                continue
            left = index+1
            right = length-1
            while left < right:
                total = value + nums[left] + nums[right]
                if total == 0:
                    # We are done
                    result.append([nums[index],nums[left], nums[right]])
                    left += 1
                    # Find non repeating next index
                    while left < right and nums[left] == nums[left-1]:
                        left += 1
                elif total < 0:
                    left += 1
                else:
                    right -= 1
        return result
                    
```