Create 3Sum.py

Author: Ram-95

3Sum.py

@@ -0,0 +1,63 @@
+# Solution - 1 | O(N**2) Time and O(N) Space
+class Solution:
+    def threeSum(self, nums):
+        nums.sort()
+        result = []
+        for left in range(len(nums) - 2): # renamed this to left because this will always be the leftmost pointer in the triplet
+            if left > 0 and nums[left] == nums[left - 1]: # this step makes sure that we do not have any duplicates in our result output
+                continue 
+            mid = left + 1 # renamed this to mid because this is the pointer that is between the left and right pointers
+            right = len(nums) - 1
+            while mid < right:
+                curr_sum = nums[left] + nums[mid] + nums[right]
+                if curr_sum < 0:
+                    mid += 1 
+                elif curr_sum > 0:
+                    right -= 1
+                else:
+                    result.append([nums[left], nums[mid], nums[right]])
+                    while mid < right and nums[mid] == nums[mid + 1]: # Another conditional for not calculating duplicates
+                        mid += 1
+                    while mid < right and nums[right] == nums[right - 1]: # Avoiding duplicates check
+                        right -= 1
+                    mid += 1
+                    right -= 1
+        return result
+                        
+        
+
+
+
+# Solution - 2 | O(N**2) Time and O(N) Space
+from collections import Counter
+class Solution:
+    def threeSum(self, nums: List[int]) -> List[List[int]]:
+        visited = set()
+        ans, n = set(), len(nums)
+        def two_sum(arr, target):
+            c = Counter(arr)
+            res = set()
+            for i in arr:
+                x = target - i
+                if x in c:
+                    if x == i and c[x] > 1:
+                        if (i,x) not in res and (x,i) not in res:
+                            res.add((i, x))
+                    elif x != i:
+                        if (i,x) not in res and (x,i) not in res:
+                            res.add((i, x))                    
+            return res
+        
+        
+        for i,v in enumerate(nums):
+            if v not in visited:
+                t_arr = nums[:i] + nums[i+1:]
+                ts = two_sum(t_arr, -v)
+                if ts:
+                    for item in ts:
+                        t = [v] + list(item)
+                        t.sort()
+                        ans.add(tuple(t))
+                visited.add(v)
+            
+        return ans