Solution two-pointers 1

3sum.py

@@ -0,0 +1,37 @@
+# // Time Complexity : O(nlogn + n^2) => O(n^2)
+# // Space Complexity : sorting takes O(n) 
+# // Did this code successfully run on Leetcode : Yes
+# // Any problem you faced while coding this : I was trying to do twosum with just rest of the array and taregt as 0-nums[i]. 
+# It was hard to get to the point where I should try and form the result set of 3 numbers while handling 2 sum, instead of just getting the 2 nums other than i and then figuring out to remove duplicates. 
+
+class Solution(object):
+    def threeSum(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: List[List[int]]
+        """
+        resultset=[]
+        nums.sort()
+        i=0
+        while i<len(nums):
+            if nums[i]>0: break
+            if i!=0 and nums[i-1]==nums[i]:
+                i+=1
+            else:
+                start=i+1
+                end=len(nums)-1
+                while start< end:
+                    s=nums[i]+nums[start]+nums[end]
+                    if s==0:                        
+                        resultset.append([nums[i],nums[start],nums[end]])
+                        start+=1
+                        end-=1
+                        while start<end and nums[start]==nums[start-1]:
+                            start+=1
+                    elif s <0:
+                        start+=1
+                    else:
+                        end-=1
+                i+=1
+
+        return resultset

maxwater.py

@@ -0,0 +1,27 @@
+# // Time Complexity : O(n)
+# // Space Complexity : O(1)
+# // Did this code successfully run on Leetcode : Yes
+# // Any problem you faced while coding this : No
+
+class Solution(object):
+    def maxArea(self, height):
+        """
+        :type height: List[int]
+        :rtype: int
+        """
+
+        res=0
+        start=0
+        end=len(height)-1
+
+        while start<end:
+            width=end-start
+            ht = min(height[start],height[end])
+            res = max(res, width*ht)
+            if height[start]<height[end]:
+                start+=1
+            else:
+                end-=1
+
+        return res
+

sortcolors.py

@@ -0,0 +1,26 @@
+# // Time Complexity : O(n)
+# // Space Complexity : O(1)
+# // Did this code successfully run on Leetcode : Yes
+# // Any problem you faced while coding this : idea to inplace sorting did not come to me until class.
+
+class Solution(object):
+    def sortColors(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: None Do not return anything, modify nums in-place instead.
+        """
+        low=0
+        mid=0
+        high=len(nums)-1
+
+        while( mid<=high):
+            if nums[mid]==0:
+                nums[low],nums[mid]=nums[mid],nums[low]
+                low+=1
+                mid+=1
+            elif nums[mid]==2:
+                nums[high],nums[mid]=nums[mid],nums[high]
+                high-=1
+            else:
+                mid+=1
+