Data structures/arrays/triplet sum

data_structures/arrays/find_triplets_with_0_sum.py

@@ -22,3 +22,66 @@ def find_triplets_with_0_sum(nums: list[int]) -> list[list[int]]:
         list(x)
         for x in sorted({abc for abc in combinations(sorted(nums), 3) if not sum(abc)})
     ]
+
+
+def find_triplets_with_0_sum_hashing(arr: list[int]) -> list[list[int]]:
+    """
+    Function for finding the triplets with a given sum in the array using hashing.
+
+    Given a list of integers, return elements a, b, c such that a + b + c = 0.
+
+    Args:
+        nums: list of integers
+    Returns:
+        list of lists of integers where sum(each_list) == 0
+    Examples:
+        >>> find_triplets_with_0_sum_hashing([-1, 0, 1, 2, -1, -4])
+        [[-1, 0, 1], [-1, -1, 2]]
+        >>> find_triplets_with_0_sum_hashing([])
+        []
+        >>> find_triplets_with_0_sum_hashing([0, 0, 0])
+        [[0, 0, 0]]
+        >>> find_triplets_with_0_sum_hashing([1, 2, 3, 0, -1, -2, -3])
+        [[-1, 0, 1], [-3, 1, 2], [-2, 0, 2], [-2, -1, 3], [-3, 0, 3]]
+
+    Time complexity: O(N^2)
+    Auxiliary Space: O(N)
+
+    """
+    target_sum = 0
+
+    # Initialize the final output array with blank.
+    output_arr = []
+
+    # Set the initial element as arr[i].
+    for index, item in enumerate(arr[:-2]):
+        # to store second elements that can complement the final sum.
+        set_initialize = set()
+
+        # current sum needed for reaching the target sum
+        current_sum = target_sum - item
+
+        # Traverse the subarray arr[i+1:].
+        for other_item in arr[index + 1 :]:
+            # required value for the second element
+            required_value = current_sum - other_item
+
+            # Verify if the desired value exists in the set.
+            if required_value in set_initialize:
+                # finding triplet elements combination.
+                combination_array = sorted([item, other_item, required_value])
+                if combination_array not in output_arr:
+                    output_arr.append(combination_array)
+
+            # Include the current element in the set
+            # for subsequent complement verification.
+            set_initialize.add(other_item)
+
+    # Return all the triplet combinations.
+    return output_arr
+
+
+if __name__ == "__main__":
+    from doctest import testmod
+
+    testmod()