two pointers 1

Sample.py

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+// Time Complexity :
+// Space Complexity :
+// Did this code successfully run on Leetcode :
+// Any problem you faced while coding this :
+
+
+// Your code here along with comments explaining your approach
+
+## Problem1 (https://leetcode.com/problems/sort-colors/)
+## Time Complexity : O(n)
+## Space Complexity : O(1)
+# bucket sort since only 3 integers to sort
+
+class Solution:
+    def sortColors(self, nums: List[int]) -> None:
+        """
+        Do not return anything, modify nums in-place instead.
+        """
+        hashmap = {}
+        for i in nums:
+            if i not in hashmap:
+                hashmap[i] = 0
+            hashmap[i] += 1
+
+        for n in range(len(nums)):
+            if 0 in hashmap and hashmap[0] > 0:
+                nums[n] = 0
+                hashmap[0] -= 1
+            elif 1 in hashmap and hashmap[1] > 0:
+                nums[n] = 1
+                hashmap[1] -= 1
+            elif 2 in hashmap and hashmap[2] > 0:
+                nums[n] = 2
+                hashmap[2] -= 1        
+
+## Problem2 (https://leetcode.com/problems/3sum/)
+## Time Complexity : O(nlogn)
+## Space Complexity : O(1)
+# Hold one pivot pivot and then run 2sum
+
+class Solution:
+    def threeSum(self, nums: list[int]) -> list[list[int]]:
+        def twoSum(nums,pivot,res):
+            hashset = set()
+            i = pivot + 1
+            while i < len(nums):
+            	# a+b+c=0 --> c = -a-b -> a is the pivot, b is the current number and we are finding complement
+                comp = -nums[pivot] - nums[i]
+                if comp in hashset:
+                    res.append([nums[pivot],nums[i],comp])
+                    while i + 1 < len(nums) and nums[i] == nums[i+1]:
+                        i += 1
+                hashset.add(nums[i])
+                i += 1
+
+        res = []
+        nums.sort()
+        prev = float(inf)
+
+        for pivot in range(0,len(nums)):
+            if nums[pivot] > 0:
+                break
+            if pivot == 0 or nums[pivot-1] != nums[pivot]:
+                twoSum(nums,pivot,res)
+        return res
+
+
+## Problem3 (https://leetcode.com/problems/container-with-most-water/)
+## Time Complexity : O(n)
+## Space Complexity : O(1)
+## Did this code successfully run on Leetcode : Yes
+
+class Solution:
+    def maxArea(self, height: List[int]) -> int:
+        #brute force = nested for loop
+
+        maxarea = 0
+        i,j = 0,len(height)-1
+
+        while i < j:
+            area = min(height[i],height[j]) * abs(j-i)
+            maxarea = max(area,maxarea)
+            if height[i] <= height[j]:
+                i += 1
+            elif height[j] < height[i]:
+                j -= 1
+
+        return maxarea