Merge pull request deutranium#93 from Hamzakam/exponential-search

Create readme.md

Author: deutranium

searchingAlgo/exponentialSearch/README.md

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+
+# Exponential Search
+
+ - Exponential search allows for searching through a sorted, unbounded list for a specified input value.
+ - Time Complexity:
+	 - Worst Case Complexity:_O_(log _i_)
+	 - Best Case Complexity:_O_(1)
+	 - Average Case Complexity:_O_(log _i_)
+- Worst Case Space Complexity:_O_(1)
+- Exponential Search will run in  _O_(log _i_) time, where  _i_  is the index of the element being searched for in the list, whereas binary search would run in  _O_(log _n_) time, where  _n_  is the number of elements in the list.
+- Works only on sorted lists.
+
+### Logic
+
+ 1.  Find range where element is present
+2.  Do Binary Search in above found range.
+ 3. Pseudo Code:	
+
+		   function exponentialSearch(arr, x, lo, hi):
+			if arr[hi] >= x:
+				return(binarySearch(arr, x, lo, hi + 1))
+			else:
+				return(exponentialSearch(arr, x, hi, hi * 2))
+
+			function binarySearch(arr, x, lo, hi):
+				index = (lo + hi)/2
+				if x = arr[index]
+					return index
+				else if x > arr[index]:
+					return binarySearch(arr, x, index, hi)
+				else:
+					return binarySearch(arr, x, 0, index)
+
+###  Instruction for Running code:
+
+- Python
+
+```
+python3 exponentialSearch.py
+```