[Add] Leetcode > 18. 4Sum

Author: Joie-Kim

Leetcode/four_sum.py

@@ -0,0 +1,30 @@
+class Solution:
+    def fourSum(self, nums: List[int], target: int) -> List[List[int]]:
+        results = []
+        nums.sort()
+        
+        for i in range(len(nums)-2):
+            if i > 0 and nums[i] == nums[i-1]: continue
+            
+            left1, right = i+1, len(nums)-1
+            while left1 < right:
+                left2, right = left1+1, len(nums)-1
+                while left2 < right:
+                    sum = nums[i] + nums[left1] + nums[left2] + nums[right]
+                    if sum < target:
+                        left2 += 1
+                    elif sum > target:
+                        right -= 1
+                    else:
+                        results.append((nums[i], nums[left1], nums[left2], nums[right]))
+                        while left2 < right and nums[left2] == nums[left2+1]:
+                            left2 += 1
+                        while left2 < right and nums[right] == nums[right-1]:
+                            right -= 1
+                        left2 += 1
+                        right -= 1
+                left1 += 1
+                while nums[left1] == nums[left1-1] and left1 < right:
+                    left1 += 1
+                    
+        return results