3sum solution

Author: radiantchoi

3sum/radiantchoi.py

@@ -0,0 +1,45 @@
+class Solution:
+    def twoSum(self, target: int, nums: List[int], starting: int) -> List[List[int]]:
+        left = starting
+        right = len(nums) - 1
+
+        result = []
+
+        while left < right:
+            if nums[left] + nums[right] == target:
+                result.append([nums[left], nums[right]])
+                left += 1
+                right -= 1
+
+                while left < right and nums[left] == nums[left - 1]:
+                    left += 1
+                
+                while left < right and nums[right] == nums[right + 1]:
+                    right -= 1
+            elif nums[left] + nums[right] > target:
+                right -= 1
+            else:
+                left += 1
+        
+        return result
+    
+    def kSum(self, n: int, target: int, nums: List[int], starting: int) -> List[List[int]]:
+        if n < 2 or starting == len(nums):
+            return []
+        elif n == 2:
+            return self.twoSum(target, nums, starting)
+        
+        result = []
+
+        for i in range(starting, len(nums) - n + 1):
+            if i > starting and nums[i] == nums[i - 1]:
+                continue
+            
+            for tail in self.kSum(n - 1, target - nums[i], nums, i + 1):
+                result.append([nums[i]] + tail)
+        
+        return result
+
+    def threeSum(self, nums: List[int]) -> List[List[int]]:
+        nums.sort()
+        return self.kSum(3, 0, nums, 0)