added 3sum solution

Author: yayyz

3sum/yayyz.py

@@ -0,0 +1,25 @@
+class Solution:
+    def threeSum(self, nums: List[int]) -> List[List[int]]:
+        nums.sort()
+        result = []
+        for i in range(len(nums)):
+            if i > 0 and nums[i] == nums[i - 1]:
+                continue 
+                
+            left = i + 1
+            right = len(nums) - 1
+            while left < right: 
+                total = nums[i] + nums[left] + nums[right]
+                if total < 0: 
+                    left += 1
+                elif total > 0:
+                    right -= 1
+                else: 
+                    result.append([nums[i], 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
+        return result