D. J.:

- Added the leetcode problem and solution for 18

Author: nobodyPerfecZ

README.md

@@ -80,6 +80,7 @@
 - [15 3Sum](https://leetcode.com/problems/3sum/description/)
 - [16 3Sum Closest](https://leetcode.com/problems/3sum-closest/description/)
 - [17 Letter Combinations of a Phone Number](https://leetcode.com/problems/letter-combinations-of-a-phone-number/description/)
+- [18 4Sum](https://leetcode.com/problems/4sum/description/)
 - [19 Remove Nth Node From End of List](https://leetcode.com/problems/remove-nth-node-from-end-of-list/description/)
 - [20 Valid Parentheses](https://leetcode.com/problems/valid-parentheses/description/)
 - [21 Merge Two Sorted Lists](https://leetcode.com/problems/merge-two-sorted-lists/description/)

awesome_python_leetcode/_18_four_sum.py

@@ -0,0 +1,44 @@
+from typing import List
+
+
+class Solution:
+    """Base class for all LeetCode Problems."""
+
+    def fourSum(self, nums: List[int], target: int) -> List[List[int]]:
+        """
+        Given an array nums of n integers, return an array of all the unique quadruplets
+        [nums[a], nums[b], nums[c], nums[d]] such that:
+
+        - 0 <= a, b, c, d < n
+        - a, b, c, and d are distinct.
+        - nums[a] + nums[b] + nums[c] + nums[d] == target
+
+        You may return the answer in any order.
+        """
+        nums = sorted(nums)
+        fourSums = []
+        i = 0
+        while i < len(nums) - 3:
+            if i > 0 and nums[i] == nums[i - 1]:
+                i += 1
+                continue
+            j = i + 1
+            while j < len(nums) - 2:
+                if j > i + 1 and nums[j] == nums[j - 1]:
+                    j += 1
+                    continue
+                left, right = j + 1, len(nums) - 1
+                while left < right:
+                    fourSum = nums[i] + nums[j] + nums[left] + nums[right]
+                    if fourSum > target:
+                        right -= 1
+                    elif fourSum < target:
+                        left += 1
+                    else:
+                        fourSums.append([nums[i], nums[j], nums[left], nums[right]])
+                        left += 1
+                        while left < right and nums[left] == nums[left - 1]:
+                            left += 1
+                j += 1
+            i += 1
+        return fourSums

tests/test_18_four_sum.py

@@ -0,0 +1,19 @@
+from typing import List
+
+import pytest
+
+from awesome_python_leetcode._18_four_sum import Solution
+
+
+@pytest.mark.parametrize(
+    argnames=["nums", "target", "expected"],
+    argvalues=[
+        ([1, 0, -1, 0, -2, 2], 0, [[-2, -1, 1, 2], [-2, 0, 0, 2], [-1, 0, 0, 1]]),
+        ([2, 2, 2, 2, 2], 8, [[2, 2, 2, 2]]),
+        ([-2, -1, -1, 1, 1, 2, 2], 0, [[-2, -1, 1, 2], [-1, -1, 1, 1]]),
+    ],
+)
+def test_func(nums: List[int], target: int, expected: List[List[int]]):
+    """Tests the solution of a LeetCode problem."""
+    four_sums = Solution().fourSum(nums, target)
+    assert four_sums == expected