Search an element in a sorted and rotated array.cpp

/* C++ Program to search an element 
in a sorted and pivoted array*/
#include <bits/stdc++.h> 
using namespace std; 

/* Standard Binary Search function*/
int binarySearch(int arr[], int low, 
				int high, int key) 
{ 
if (high < low) 
	return -1; 
	
int mid = (low + high)/2; /*low + (high - low)/2;*/
if (key == arr[mid]) 
	return mid; 
	
if (key > arr[mid]) 
	return binarySearch(arr, (mid + 1), high, key); 
	
// else 
	return binarySearch(arr, low, (mid -1), key); 
} 

/* Function to get pivot. For array 3, 4, 5, 6, 1, 2 
it returns 3 (index of 6) */
int findPivot(int arr[], int low, int high) 
{ 
// base cases 
if (high < low) return -1; 
if (high == low) return low; 

int mid = (low + high)/2; /*low + (high - low)/2;*/
if (mid < high && arr[mid] > arr[mid + 1]) 
	return mid; 
	
if (mid > low && arr[mid] < arr[mid - 1]) 
	return (mid-1); 
	
if (arr[low] >= arr[mid]) 
	return findPivot(arr, low, mid-1); 
	
return findPivot(arr, mid + 1, high); 
} 

/* Searches an element key in a pivoted 
sorted array arr[] of size n */
int pivotedBinarySearch(int arr[], int n, int key) 
{ 
int pivot = findPivot(arr, 0, n-1); 

// If we didn't find a pivot, 
// then array is not rotated at all 
if (pivot == -1) 
	return binarySearch(arr, 0, n-1, key); 

// If we found a pivot, then first compare with pivot 
// and then search in two subarrays around pivot 
if (arr[pivot] == key) 
	return pivot; 
	
if (arr[0] <= key) 
	return binarySearch(arr, 0, pivot-1, key); 
	
	return binarySearch(arr, pivot+1, n-1, key); 
} 

/* Driver program to check above functions */
int main() 
{ 
// Let us search 3 in below array 
int arr1[] = {5, 6, 7, 8, 9, 10, 1, 2, 3}; 
int n = sizeof(arr1)/sizeof(arr1[0]); 
int key = 3; 
	
// Function calling 
cout << "Index of the element is : " << 
		pivotedBinarySearch(arr1, n, key); 
			
return 0; 
} 
// source : gfg