Time: 413 ms (88.42%), Space: 18.1 MB (37.73%) - LeetHub

Author: hogan-tech

0259-3sum-smaller/0259-3sum-smaller.py

@@ -0,0 +1,35 @@
+# time complexity: O(n^2)
+# space completity: O(1)
+from typing import List
+
+
+class Solution:
+    def threeSumSmaller(self, nums: List[int], target: int) -> int:
+        result = 0
+        nums.sort()
+        for i in range(len(nums) - 1):
+            result += self.twoSumSmaller(nums, i + 1, target - nums[i])
+        return result
+
+    def twoSumSmaller(self, nums: List[int], startIdx: int, target: int) -> int:
+        left = startIdx
+        right = len(nums) - 1
+        result = 0
+        while left < right:
+            if nums[left] + nums[right] < target:
+                result += right - left
+                left += 1
+            else:
+                right -= 1
+        return result
+
+
+nums = [-2, 0, 1, 3]
+target = 2
+print(Solution().threeSumSmaller(nums, target))
+nums = []
+target = 0
+print(Solution().threeSumSmaller(nums, target))
+nums = [0]
+target = 0
+print(Solution().threeSumSmaller(nums, target))