added readme file

Challenge-3/solution.py

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+class Solution(object):
+    def maxProfit(self, prices):
+        """
+        :type prices: List[int]
+        :rtype: int
+        """
+        left = 0
+        right = 1
+        maxprofit = 0
+        while right < len(prices):
+            if prices[right] > prices[left]:
+                maxprofit = max(prices[right] - prices[left], maxprofit)
+            else:
+                left = right
+            right += 1
+        return maxprofit

Challenge-4/solution.py

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+class Solution(object):
+    def containsDuplicate(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: bool
+        """
+        dic = {}
+        for i, n in enumerate(nums):
+            if n in dic:
+                return True
+            dic[n] = i
+        return False

Challenge-5/solution.py

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

Challenge-6/solution.py

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+class Solution(object):
+    def productExceptSelf(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: List[int]
+        """
+        res = [1] * len(nums)
+        prefix = 1
+        for i in range(1, len(nums)):
+            prefix = prefix * nums[i-1]
+            res[i] = prefix
+        suffix = 1
+        for j in range(len(nums) - 2, -1, -1):
+            suffix = suffix * nums[j+1]
+            res[j] = res[j] * suffix 
+        return res

Challenge-7/solution.py

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+class Solution(object):
+    def maxSubArray(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: int
+        """
+        maxsum = nums[0]
+        cursum = nums[0]
+        for i in range(1, len(nums)):
+            cursum = max(cursum + nums[i], nums[i])
+            maxsum = max(maxsum, cursum)
+        return maxsum

Challenge-8/solution.py

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+class Solution(object):
+    def maxProduct(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: int
+        """
+        res = nums[0]
+        maxsum = 1
+        minsum = 1
+        for i in nums:
+            curpro = maxsum * i
+            maxsum = max(curpro, minsum * i, i)
+            minsum = min(curpro, minsum * i, i)
+            res = max(res, maxsum)
+        return res

Challenge-9/solution.py

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+class Solution(object):
+    def findMin(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: int
+        """
+        lo, hi = 0, len(nums) - 1
+        while lo < hi:
+            if nums[lo] < nums[hi]:
+                return nums[lo]
+
+            mid = (lo + hi) // 2
+            if nums[mid] > nums[hi]:
+                lo = mid + 1
+            else:
+                hi = mid

challenge-1/README.md

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+Name : Rashad M
+Email : rashadbasheer.m@gmail.com

challenge-2/two-sum.py

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+def two_sum(nums, target):
+    """
+    :type nums: List[int]
+    :type k: int
+    :rtype: float
+    """
+    num_dict = {}
+    n = len(nums)
+    for i in range(n):
+        dif = target - nums[i]
+        if dif in num_dict:
+            return [num_dict[dif], i]
+        num_dict[nums[i]] = i