Added solution for Two Sum

Challenge-1/two-sum.py

@@ -0,0 +1,15 @@
+class Solution(object):
+    def twoSum(self, nums, target):
+        """
+        :type nums: List[int]
+        :type target: int
+        :rtype: List[int]
+        """
+        prev_map = dict()
+        for i, num in enumerate(nums):
+            if target - num in prev_map:
+                return(i , prev_map[target-num])
+            else:
+                prev_map[num] = i
+
+        return -1

Challenge-2/maxprofit.py

@@ -0,0 +1,18 @@
+class Solution(object):
+    def maxProfit(self, prices):
+        """
+        :type prices: List[int]
+        :rtype: int
+        """
+        min_price = prices[0]
+        max_price = 0
+        profit = 0
+
+        for price in prices:
+            if price < min_price:
+                min_price = price
+                max_price = price
+            elif price > max_price:
+                max_price = price
+                profit = max(max_price - min_price, profit) 
+        return profit

Challenge-3/duplicatefinding.py

@@ -0,0 +1,3 @@
+class Solution(object):
+    def containsDuplicate(self, nums):
+        return len(nums) != len(set(nums))

Challenge-4/sumofintegers.py

@@ -0,0 +1,14 @@
+class Solution(object):
+    def getSum(self, a, b):
+        """
+        :type a: int
+        :type b: int
+        :rtype: int
+        """
+        bitshortner = 0xffffffff
+
+        while(b & bitshortner) > 0:
+            carry = (a&b)<<1
+            a =(a^b)
+            b = carry
+        return (a&bitshortner) if b > 0 else a

Challenge-6/productofarray.py

@@ -0,0 +1,12 @@
+def productExceptSelf(nums):
+    res = [1]* len(nums)
+
+    prefix = 1
+    for i in range(len(nums)):
+        res[i] = prefix
+        prefix = prefix*nums[i]
+    postfix = 1
+    for i in range(len(nums) -1,-1,-1):
+        res[i]= res[i]*postfix
+        postfix = postfix * nums[i]
+    return res

Challenge-7/maxsubarray.py

@@ -0,0 +1,14 @@
+class Solution(object):
+    def maxSubArray(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: int
+        """
+        maxsubarr = nums[0]
+        carrsum = 0
+        for n in nums:
+            if carrsum < 0:
+                carrsum = 0
+            carrsum += n
+            maxsubarr = max(maxsubarr , carrsum) 
+        return maxsubarr