From f44509b5c45fe76f2620b22766c35d1da89f9928 Mon Sep 17 00:00:00 2001
From: alekh08 <137406174+alekh08@users.noreply.github.com>
Date: Sun, 23 Feb 2025 17:34:29 +0530
Subject: [PATCH 1/4] Added Two pointer approach.
---
.../arrays/find_triplets_with_0_sum.py | 75 +++++++++++++++++++
1 file changed, 75 insertions(+)
diff --git a/data_structures/arrays/find_triplets_with_0_sum.py b/data_structures/arrays/find_triplets_with_0_sum.py
index 52e521906873..7d598c088483 100644
--- a/data_structures/arrays/find_triplets_with_0_sum.py
+++ b/data_structures/arrays/find_triplets_with_0_sum.py
@@ -81,7 +81,82 @@ def find_triplets_with_0_sum_hashing(arr: list[int]) -> list[list[int]]:
return output_arr
+# Two pointer approach to find triplets with zero sum
+
+"""
+Why is it the best?
+1. Faster than brute force due to sorting and then two pointers scanning.
+
+2. No extra space needed (except for sorting).
+
+3. Handles Duplicate efficiently by skipping repeated values.
+"""
+def find_triplets_with_0_sum_two_pointer(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_two_pointer([-1, 0, 1, 2, -1, -4])
+ [[-1, 0, 1], [-1, -1, 2]]
+ >>> find_triplets_with_0_sum_two_pointer([])
+ []
+ >>> find_triplets_with_0_sum_two_pointer([0, 0, 0])
+ [[0, 0, 0]]
+ >>> find_triplets_with_0_sum_two_pointer([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(1) (excluding output storage)
+
+ """
+
+ # Step 1: Sort the array to facilitate the two pointer approach
+ nums.sort()
+ triplets = [] # list to store the valid triplets
+ n = len(nums)
+
+ # Step 2: iterate through the array, fixing one number at a time
+ for i in range(n - 2): # We need atleast 3 elements for a triplet
+ # skip duplicate elements for the first number
+ if i > 0 and nums[i] == nums[i - 1]:
+ continue #Move to the distinct number
+
+ # Step 3: Use the two pointer technique to find pairs that sum up to -nums[i]
+ left, right = i + 1, n - 1 # Initialize two pointers
+ while left < right:
+ total = nums[i] + nums[left] + nums[right] #Calculate sum of three numbers
+
+ if total == 0:
+ # If the sum is zero, we found a valid triplet
+ triplets.append([nums[i], nums[left], nums[right]])
+
+ # Move both pointers to look for the next unique pair
+ left += 1
+ right -= 1
+
+ # skip duplicate values for the second and third numbers
+ while left < right and nums[left] == nums[left - 1]:
+ left += 1
+ while left < right and nums[right] == nums[right + 1]:
+ right -= 1
+
+ elif total < 0:
+ # If sum is less than zero, move the left pointer to the right
+ left += 1
+ else:
+ # If sum is greater than zero, move the right pointer to the left
+ right -= 1
+ return triplets
+
+
if __name__ == "__main__":
from doctest import testmod
testmod()
+
From ad7f983149ea475cc5951687a2a98b49a6e78f36 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
<66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Sun, 23 Feb 2025 12:10:02 +0000
Subject: [PATCH 2/4] [pre-commit.ci] auto fixes from pre-commit.com hooks
for more information, see https://pre-commit.ci
---
data_structures/arrays/find_triplets_with_0_sum.py | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/data_structures/arrays/find_triplets_with_0_sum.py b/data_structures/arrays/find_triplets_with_0_sum.py
index 7d598c088483..5ebc42d6ca7f 100644
--- a/data_structures/arrays/find_triplets_with_0_sum.py
+++ b/data_structures/arrays/find_triplets_with_0_sum.py
@@ -91,6 +91,8 @@ def find_triplets_with_0_sum_hashing(arr: list[int]) -> list[list[int]]:
3. Handles Duplicate efficiently by skipping repeated values.
"""
+
+
def find_triplets_with_0_sum_two_pointer(arr: list[int]) -> list[list[int]]:
"""
Function for finding the triplets with a given sum in the array using hashing.
@@ -122,15 +124,15 @@ def find_triplets_with_0_sum_two_pointer(arr: list[int]) -> list[list[int]]:
n = len(nums)
# Step 2: iterate through the array, fixing one number at a time
- for i in range(n - 2): # We need atleast 3 elements for a triplet
+ for i in range(n - 2): # We need atleast 3 elements for a triplet
# skip duplicate elements for the first number
if i > 0 and nums[i] == nums[i - 1]:
- continue #Move to the distinct number
+ continue # Move to the distinct number
# Step 3: Use the two pointer technique to find pairs that sum up to -nums[i]
left, right = i + 1, n - 1 # Initialize two pointers
while left < right:
- total = nums[i] + nums[left] + nums[right] #Calculate sum of three numbers
+ total = nums[i] + nums[left] + nums[right] # Calculate sum of three numbers
if total == 0:
# If the sum is zero, we found a valid triplet
@@ -159,4 +161,3 @@ def find_triplets_with_0_sum_two_pointer(arr: list[int]) -> list[list[int]]:
from doctest import testmod
testmod()
-
From 478cc36b433964162bd120c40584255b40da9ca9 Mon Sep 17 00:00:00 2001
From: alekh08 <137406174+alekh08@users.noreply.github.com>
Date: Sun, 23 Feb 2025 18:01:21 +0530
Subject: [PATCH 3/4] Refactor: Renamed variable arr to nums for clarity
---
data_structures/arrays/find_triplets_with_0_sum.py | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/data_structures/arrays/find_triplets_with_0_sum.py b/data_structures/arrays/find_triplets_with_0_sum.py
index 5ebc42d6ca7f..0791fa4188a6 100644
--- a/data_structures/arrays/find_triplets_with_0_sum.py
+++ b/data_structures/arrays/find_triplets_with_0_sum.py
@@ -91,9 +91,7 @@ def find_triplets_with_0_sum_hashing(arr: list[int]) -> list[list[int]]:
3. Handles Duplicate efficiently by skipping repeated values.
"""
-
-
-def find_triplets_with_0_sum_two_pointer(arr: list[int]) -> list[list[int]]:
+def find_triplets_with_0_sum_two_pointer(nums: list[int]) -> list[list[int]]:
"""
Function for finding the triplets with a given sum in the array using hashing.
From 54ccb53361a47a18b93a0f0b645881861e3457c2 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
<66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Sun, 23 Feb 2025 12:35:53 +0000
Subject: [PATCH 4/4] [pre-commit.ci] auto fixes from pre-commit.com hooks
for more information, see https://pre-commit.ci
---
data_structures/arrays/find_triplets_with_0_sum.py | 2 ++
1 file changed, 2 insertions(+)
diff --git a/data_structures/arrays/find_triplets_with_0_sum.py b/data_structures/arrays/find_triplets_with_0_sum.py
index 0791fa4188a6..a5fdda097e60 100644
--- a/data_structures/arrays/find_triplets_with_0_sum.py
+++ b/data_structures/arrays/find_triplets_with_0_sum.py
@@ -91,6 +91,8 @@ def find_triplets_with_0_sum_hashing(arr: list[int]) -> list[list[int]]:
3. Handles Duplicate efficiently by skipping repeated values.
"""
+
+
def find_triplets_with_0_sum_two_pointer(nums: list[int]) -> list[list[int]]:
"""
Function for finding the triplets with a given sum in the array using hashing.