From f143adb639ec5ea9ffa289ba1bab871362c3dbc4 Mon Sep 17 00:00:00 2001
From: Manas Bhilare <69368910+Manas146@users.noreply.github.com>
Date: Wed, 6 Oct 2021 11:57:11 +0530
Subject: [PATCH 1/4] Added 4Sums readme file and code

---
 0018/4Sums.py  | 18 ++++++++++++++++++
 0018/README.md | 27 +++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)
 create mode 100644 0018/4Sums.py
 create mode 100644 0018/README.md

diff --git a/0018/4Sums.py b/0018/4Sums.py
new file mode 100644
index 0000000..ea7d0ce
--- /dev/null
+++ b/0018/4Sums.py
@@ -0,0 +1,18 @@
+class Solution:
+    def fourSum(self, nums: List[int], target: int) -> List[List[int]]:
+        ans = set()
+        nums.sort()
+        for i in range(len(nums) - 3):
+            for j in range(i + 1, len(nums) - 2):
+                lo = j + 1
+                hi = len(nums) - 1
+                while lo < hi:
+                    s = nums[i] + nums[j] + nums[lo] + nums[hi]
+                    if s == target:
+                        ans.add((nums[i], nums[j], nums[lo], nums[hi]))
+                        lo += 1
+                    elif s < target:
+                        lo += 1
+                    else:
+                        hi -= 1
+        return list(ans)
\ No newline at end of file
diff --git a/0018/README.md b/0018/README.md
new file mode 100644
index 0000000..8ed8deb
--- /dev/null
+++ b/0018/README.md
@@ -0,0 +1,27 @@
+# 4Sums
+
+Given an array nums of n integers, return an array of all the unique quadruplets [nums[a], nums[b], nums[c], nums[d]] such that:
+
+0 <= a, b, c, d < n
+a, b, c, and d are distinct.
+nums[a] + nums[b] + nums[c] + nums[d] == target
+You may return the answer in any order.
+
+ 
+
+## Example 1:
+
+Input: nums = [1,0,-1,0,-2,2], target = 0
+Output: [[-2,-1,1,2],[-2,0,0,2],[-1,0,0,1]]
+
+## Example 2:
+
+Input: nums = [2,2,2,2,2], target = 8
+Output: [[2,2,2,2]]
+ 
+
+## Constraints:
+
+1 <= nums.length <= 200
+-109 <= nums[i] <= 109
+-109 <= target <= 109
\ No newline at end of file

From afe36f2072369037bf36c2c6475bef1ab02da9bd Mon Sep 17 00:00:00 2001
From: Manas Bhilare <69368910+Manas146@users.noreply.github.com>
Date: Wed, 6 Oct 2021 11:57:46 +0530
Subject: [PATCH 2/4] Update README.md

---
 0018/README.md | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/0018/README.md b/0018/README.md
index 8ed8deb..d0a59ca 100644
--- a/0018/README.md
+++ b/0018/README.md
@@ -11,12 +11,18 @@ You may return the answer in any order.
 
 ## Example 1:
 
-Input: nums = [1,0,-1,0,-2,2], target = 0
+Input: nums = [1,0,-1,0,-2,2], 
+
+target = 0
+
 Output: [[-2,-1,1,2],[-2,0,0,2],[-1,0,0,1]]
 
 ## Example 2:
 
-Input: nums = [2,2,2,2,2], target = 8
+Input: nums = [2,2,2,2,2], 
+
+target = 8
+
 Output: [[2,2,2,2]]
  
 
@@ -24,4 +30,4 @@ Output: [[2,2,2,2]]
 
 1 <= nums.length <= 200
 -109 <= nums[i] <= 109
--109 <= target <= 109
\ No newline at end of file
+-109 <= target <= 109

From 939d7aca16c63ceccd5f98a14dc13d4d1df96c1c Mon Sep 17 00:00:00 2001
From: Manas Bhilare <69368910+Manas146@users.noreply.github.com>
Date: Wed, 6 Oct 2021 12:00:43 +0530
Subject: [PATCH 3/4] Update README.md

---
 0018/README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/0018/README.md b/0018/README.md
index d0a59ca..75d0a07 100644
--- a/0018/README.md
+++ b/0018/README.md
@@ -1,4 +1,4 @@
-# 4Sums
+# 4Sum
 
 Given an array nums of n integers, return an array of all the unique quadruplets [nums[a], nums[b], nums[c], nums[d]] such that:
 

From e385c7b312dbcb3e19f9ea1f2ae98cd1f517d3ed Mon Sep 17 00:00:00 2001
From: Manas Bhilare <69368910+Manas146@users.noreply.github.com>
Date: Thu, 7 Oct 2021 21:37:43 +0530
Subject: [PATCH 4/4] Updated 4Sum code

---
 0018/4Sum.py  | 33 +++++++++++++++++++++++++++++++++
 0018/4Sums.py | 18 ------------------
 2 files changed, 33 insertions(+), 18 deletions(-)
 create mode 100644 0018/4Sum.py
 delete mode 100644 0018/4Sums.py

diff --git a/0018/4Sum.py b/0018/4Sum.py
new file mode 100644
index 0000000..f58cb8f
--- /dev/null
+++ b/0018/4Sum.py
@@ -0,0 +1,33 @@
+# Two Pointers approach
+
+class Solution:
+    def fourSum(self, nums: List[int], target: int) -> List[List[int]]:
+	
+        def kSum(nums: List[int], target: int, k: int) -> List[List[int]]:
+            res = []
+            if len(nums) == 0 or nums[0] * k > target or target > nums[-1] * k:
+                return res
+            if k == 2:
+                return twoSum(nums, target)
+    
+            for i in range(len(nums)):
+                if i == 0 or nums[i - 1] != nums[i]:
+                    for subset in kSum(nums[i + 1:], target - nums[i], k - 1):
+                        res.append([nums[i]] + subset)
+    
+            return res
+
+        def twoSum(nums: List[int], target: int) -> List[List[int]]:
+            res = []
+            s = set()
+    
+            for i in range(len(nums)):
+                if len(res) == 0 or res[-1][1] != nums[i]:
+                    if target - nums[i] in s:
+                        res.append([target - nums[i], nums[i]])
+                s.add(nums[i])
+    
+            return res
+
+        nums.sort()
+        return kSum(nums, target, 4)
diff --git a/0018/4Sums.py b/0018/4Sums.py
deleted file mode 100644
index ea7d0ce..0000000
--- a/0018/4Sums.py
+++ /dev/null
@@ -1,18 +0,0 @@
-class Solution:
-    def fourSum(self, nums: List[int], target: int) -> List[List[int]]:
-        ans = set()
-        nums.sort()
-        for i in range(len(nums) - 3):
-            for j in range(i + 1, len(nums) - 2):
-                lo = j + 1
-                hi = len(nums) - 1
-                while lo < hi:
-                    s = nums[i] + nums[j] + nums[lo] + nums[hi]
-                    if s == target:
-                        ans.add((nums[i], nums[j], nums[lo], nums[hi]))
-                        lo += 1
-                    elif s < target:
-                        lo += 1
-                    else:
-                        hi -= 1
-        return list(ans)
\ No newline at end of file