feat(work): add new LeetCode solution files for 1426, 1832, 344, and 15

work/3/Medium/Array/15.3sum.py

@@ -0,0 +1,89 @@
+"""
+15. 3Sum
+Difficulty: Medium
+https://leetcode.com/problems/3sum/
+
+──────────────────────────────────────────────────
+
+Given an integer array nums, return all the triplets [nums[i],
+nums[j], nums[k]] such that i != j, i != k, and j != k, and nums[i] +
+nums[j] + nums[k] == 0.
+
+Notice that the solution set must not contain duplicate triplets.
+
+
+
+Example 1:
+
+Input: nums = [-1,0,1,2,-1,-4]
+Output: [[-1,-1,2],[-1,0,1]]
+Explanation:
+nums[0] + nums[1] + nums[2] = (-1) + 0 + 1 = 0.
+nums[1] + nums[2] + nums[4] = 0 + 1 + (-1) = 0.
+nums[0] + nums[3] + nums[4] = (-1) + 2 + (-1) = 0.
+The distinct triplets are [-1,0,1] and [-1,-1,2].
+Notice that the order of the output and the order of the triplets
+does not matter.
+
+Example 2:
+
+Input: nums = [0,1,1]
+Output: []
+Explanation: The only possible triplet does not sum up to 0.
+
+Example 3:
+
+Input: nums = [0,0,0]
+Output: [[0,0,0]]
+Explanation: The only possible triplet sums up to 0.
+
+
+
+Constraints:
+
+        • 3 <= nums.length <= 3000
+
+        • -10^5 <= nums[i] <= 10^5
+"""
+
+
+class Solution:
+    def threeSum(self, nums: list[int]) -> list[list[int]]:
+        nums.sort()
+        result = []
+        n = len(nums)
+
+        for i in range(n):
+            # skip all zero
+            if i > 0 and nums[i] == nums[i - 1]:
+                continue
+
+            # two pointers
+            left = i + 1
+            right = n - 1
+            target = -nums[i]
+
+            while left < right:
+                current = nums[left] + nums[right]
+
+                if current == target:
+                    result.append([nums[i], nums[left], nums[right]])
+
+                    # skip duplicates
+                    while left < right and nums[left] == nums[left + 1]:
+                        left += 1
+                    while left < right and nums[right] == nums[right - 1]:
+                        right -= 1
+
+                    # shift pointers
+                    left += 1
+                    right -= 1
+
+                # since sorted, if current < target, then move left
+                elif current < target:
+                    left += 1
+                # since sorted, if current > target, then move right
+                else:
+                    right -= 1
+
+        return result