added leetcode array solutions in python

Author: gitarthasarma

leetcode/python/arrays/first_last_position_sorted_array.py

@@ -0,0 +1,49 @@
+class Solution(object):
+    def searchRange(self, nums, target):
+        """
+        :type nums: List[int]
+        :type target: int
+        :rtype: List[int]
+        """
+        res= [-1]*2
+        lo= 0
+        n= len(nums)
+        hi= n-1
+        if (n==0):
+            return res
+        while (lo<hi):
+            mid= lo + (hi-lo)//2
+            if (nums[mid]>= target):
+                hi= mid
+            else:
+                lo= mid+1
+        
+        
+        if (nums[lo]!=target):
+            return res
+        res[0]= lo #found lower bound
+        
+        
+        lo= 0
+        hi= n-1
+        
+        while (lo<hi):
+            mid= lo +(hi-lo+1)//2
+            
+            if (nums[mid]> target):
+                hi= mid-1
+            else:
+                lo= mid
+        
+        res[1]= lo#upper bound
+        return res
+        
+        
+        
+"""
+Time complexity: O(log(n))
+Space complexity: O(1), constant space
+
+Find more details of the framework used here: https://www.topcoder.com/community/competitive-programming/tutorials/binary-search/
+
+"""

leetcode/python/arrays/search_in_rotated_sorted_array.py

@@ -0,0 +1,60 @@
+class Solution(object):
+    @staticmethod
+    def searchHelper(nums,lo,hi,target):
+        while lo<=hi:
+            mid= lo + (hi-lo)/2
+            if nums[mid]==target:
+                return mid
+            elif nums[mid]>target:
+                hi= mid-1
+            else:
+                lo= mid+1
+        return -1
+
+    def search(self, nums, target):
+        """
+        :type nums: List[int]
+        :type target: int
+        :rtype: int
+        """
+        n= len(nums)
+        lo= 0
+        hi= n-1
+        if n==0:
+            return -1
+        
+        while (lo<hi):
+            mid= lo+ (hi-lo)/2
+            if (nums[mid]<nums[0]):
+                hi= mid
+            else:
+                lo= mid+1
+        minm= lo
+        #lo is the index of the minimum element
+
+        #now we have 2 sorted(ascending) subarrays, thus do a binary search on each of them
+        
+        if (nums[lo]==target):
+            return lo
+        
+        else:
+            #simple binary search on nums[0:lo-1]
+            resIdx= Solution.searchHelper(nums, 0, minm-1, target)
+            if (resIdx!=-1):
+                return resIdx
+            #not found in the first part
+            resIdx= Solution.searchHelper(nums, minm, n-1, target)
+
+            #binary search on nums[lo+1,n-1] second part
+            
+        
+        return resIdx#target not found anywhere
+    
+    
+'''
+    Time complexity of the algorithm(asymptotically): 
+                            O(log(n)), where n is the size of the input array
+    Space complexity is constant, O(1)
+Find more details of the framework used here: https://www.topcoder.com/community/competitive-programming/tutorials/binary-search/
+
+'''