Exponential Search.cpp

#include <bits/stdc++.h> 
using namespace std; 
  
int binarySearch(int arr[], int, int, int); 
  

int exponentialSearch(int arr[], int n, int x) { 

    if (arr[0] == x) 
        return 0; 
    int i = 1; 
    while (i < n && arr[i] <= x) 
        i = i*2;
    return binarySearch(arr, i/2, min(i, n), x); 
} 

int binarySearch(int arr[], int l, int r, int x) { 
    if (r >= l){ 
        int mid = l + (r - l)/2; 

        if (arr[mid] == x) 
            return mid; 

        if (arr[mid] > x) 
            return binarySearch(arr, l, mid-1, x); 

        return binarySearch(arr, mid+1, r, x); 
    } 

    return -1; 
} 

int main(void) { 
   int arr[] = {2, 3, 4, 10, 40}; 
   int n = sizeof(arr)/ sizeof(arr[0]); 
   int x = 10; 
   int result = exponentialSearch(arr, n, x); 
   (result == -1)? printf("Element is not present in array") 
                 : printf("Element is present at index %d", 
                                                    result); 
   return 0; 
}