3sum solutions

Author: hyeri0903

3sum/hyeri0903.py

@@ -0,0 +1,39 @@
+from itertools import combinations
+
+class Solution:
+    def threeSum(self, nums: List[int]) -> List[List[int]]:
+        """
+        time complexity : O(n^2)
+        space complexity : O(1)
+        """
+        answer = []
+        nums.sort()
+        n = len(nums)
+
+        for i in range(n):
+            #skipped if nums[i] == nums[i-1] to avoid duplicate triplets
+            if i > 0 and nums[i] == nums[i-1]:
+                continue
+
+            #search with two pointer
+            left, right = i+1, n-1
+
+            while left < right:
+                total = nums[left] + nums[i] + nums[right]
+                if total == 0:
+                    answer.append([nums[left], nums[i], nums[right]])
+                    
+                    #move the pointers past duplicates
+                    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 answer