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]
+        """
+        hash_map={}
+
+        for index in range(len(nums)):
+            if nums[index] in hash_map:
+                return [hash_map[nums[index]],index]
+            else:
+                hash_map[target-nums[index]]=index
+

Challenge-2/Best-Time-to-Buy-and-Sell-Stock.py

@@ -0,0 +1,16 @@
+class Solution(object):
+    def maxProfit(self, prices):
+        """
+        :type prices: List[int]
+        :rtype: int
+        """
+        max_profit=0
+        minimum=prices[0]
+        for i in range(1,len(prices)):
+            if prices[i]>minimum:
+                max_profit=max(max_profit,prices[i]-minimum)
+            else:
+                minimum=prices[i]
+        return max_profit
+
+

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]
+        """
+        hash_map={}
+
+        for index in range(len(nums)):
+            if nums[index] in hash_map:
+                return [hash_map[nums[index]],index]
+            else:
+                hash_map[target-nums[index]]=index
+