- 3Sum DaleStudy#241

Author: ayosecu

3sum/ayosecu.py

@@ -0,0 +1,52 @@
+from typing import List
+
+class Solution:
+    """
+        - Algorithm
+            - Sort and compares with three pointers: target, left(l), right(r)
+        - Time Complexity: O(n^2), n = len(nums)
+            - sort : O(nlogn)
+            - nested two loops : O(n^2)
+            - O(nlogn + n^2) => O(n^2)
+        - Space Complexity: O(n^2) if result included.
+            - result size : result.append() called in n^2 times (nested two loops)
+    """
+    def threeSum(self, nums: List[int]) -> List[List[int]]:
+        result = []
+        nums.sort()
+        
+        n = len(nums)
+        for i in range(n - 2):
+            # skip duplicated numbers
+            if i > 0 and nums[i] == nums[i - 1]:
+                continue
+            
+            target = nums[i]
+            l, r = i + 1, n - 1
+            while l < r:
+                if nums[l] + nums[r] == -target:
+                    result.append([target, nums[l], nums[r]])                   
+                    # skip duplicated numbers
+                    while l < r and nums[l] == nums[l + 1]:
+                        l += 1
+                    while l < r and nums[r] == nums[r - 1]:
+                        r -= 1
+                    l += 1
+                    r -= 1
+                elif nums[l] + nums[r] < -target:
+                    l += 1
+                else:
+                    r -= 1
+        
+        return result
+
+tc = [
+        ([-1,0,1,2,-1,-4], [[-1,-1,2],[-1,0,1]]),
+        ([0,1,1], []),
+        ([0,0,0], [[0,0,0]])
+]
+
+for i, (nums, e) in enumerate(tc, 1):
+    sol = Solution()
+    r = sol.threeSum(nums)
+    print(f"TC {i} is Passed!" if e == r else f"TC {i} is Failed! - Expected: {e}, Result: {r}")