added solutions in leetcode/python/arrays

Author: gitarthasarma

leetcode/python/arrays/best_time_to_buy_sell_stock.py

@@ -0,0 +1,18 @@
+class Solution(object):
+    def maxProfit(self, prices):
+        """
+        :type prices: List[int]
+        :rtype: int
+        """
+        #preprocessing
+        minprice = 10000000000
+        maxprofit = 0
+        for i in range(len(prices)):
+            if prices[i] < minprice:
+                minprice = prices[i]
+            elif (prices[i] - minprice > maxprofit):
+                maxprofit = prices[i] - minprice
+        return maxprofit
+        
+            
+        

leetcode/python/arrays/container_with_most_water.py

@@ -0,0 +1,23 @@
+class Solution(object):
+    @staticmethod
+    def area(i,j,h1,h2):
+        return (j-i)*min(h1,h2)
+    def maxArea(self, height):
+        """
+        :type height: List[int]
+        :rtype: int
+        """
+        n= len(height)
+        i=0
+        j=n-1
+        res= 0
+        while (i<j):
+            res= max(res,Solution.area(i,j,height[i],height[j]))
+            #pointer calculation and movement
+            
+            if (height[i]<height[j]):
+                i+=1
+            else:
+                j-=1
+        return res
+        

leetcode/python/arrays/product_array_except_self.py

@@ -0,0 +1,31 @@
+class Solution(object):
+    def productExceptSelf(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: List[int]
+        """
+        n= len(nums)  
+        prodSoFar= 1    #running product
+        output = [nums[n-1]]*n
+        
+        #preprocessing the array
+        for i in range(n-2,-1,-1):
+            output[i]= output[i+1]*nums[i]
+        
+
+        for i in range(n-1):
+            output[i]= prodSoFar*output[i+1]
+            prodSoFar*= nums[i]
+        
+        output[n-1]= prodSoFar
+        
+        return output
+    
+    
+
+'''
+
+Time complexity of the above algorith: O(n), n is the length of the input array
+
+Space complexity: O(1), constant space
+'''