Added code for First and Last position of element in a sorted array p…

…roblem

Python/firstAndLastIndexOfAnElementInSortedArray.py

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+# https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array/
+
+def searchRange(arr, target):
+
+ n = len(arr)
+
+ # find leftIndex
+ leftIndex = -1
+
+ # start is the first index of the array
+ start = 0
+
+ # end is the last index of the array
+ end = n-1
+
+ while(start <= end):
+ # mid = (start+end)//2 
+ # (start + end) might exceed the range of integers
+
+ # better way to do this
+ mid = start + (end - start)//2
+
+ # if target element is equal to the middle element
+ if arr[mid] == target:
+
+ # potential answer is found
+ leftIndex = mid
+
+ # continue searching in left of mid
+ end = mid - 1
+
+ # target element is less than middle element
+ # search in the left
+ elif target < arr[mid]:
+ end = mid - 1
+
+ # target element is greater than middle element
+ # search in the right
+ elif target > arr[mid]:
+ start = mid + 1
+
+
+ # find rightIndex
+ rightIndex = -1
+
+ # start is the first index of the array
+ start = 0
+
+ # end is the last index of the array
+ end = n-1
+
+ while(start <= end):
+ # mid = (start+end)//2 
+ # (start + end) might exceed the range of integers
+
+ # better way to do this
+ mid = start + (end - start)//2
+
+ # if target element is equal to the middle element
+ if arr[mid] == target:
+ # potential answer is found
+ rightIndex = mid
+
+ # continue searching in right of mid
+ start = mid + 1
+
+ # target element is less than middle element
+ # search in the left
+ elif target < arr[mid]:
+ end = mid - 1
+
+ # target element is greater than middle element
+ # search in the right
+ elif target > arr[mid]:
+ start = mid + 1
+
+ return [leftIndex,rightIndex]
+
+
+