Create binary_search.py

Python/binary_search.py

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+# Python 3 program for recursive binary search.
+# Modifications needed for the older Python 2 are found in comments.
+
+# Returns index of x in arr if present, else -1
+def binary_search(arr, low, high, x):
+
+	# Check base case
+	if high >= low:
+
+		mid = (high + low) // 2
+
+		# If element is present at the middle itself
+		if arr[mid] == x:
+			return mid
+
+		# If element is smaller than mid, then it can only
+		# be present in left subarray
+		elif arr[mid] > x:
+			return binary_search(arr, low, mid - 1, x)
+
+		# Else the element can only be present in right subarray
+		else:
+			return binary_search(arr, mid + 1, high, x)
+
+	else:
+		# Element is not present in the array
+		return -1
+
+# Test array
+arr = [ 2, 3, 4, 10, 40 ]
+x = 10
+
+# Function call
+result = binary_search(arr, 0, len(arr)-1, x)
+
+if result != -1:
+	print("Element is present at index", str(result))
+else:
+	print("Element is not present in array")