binary search.cpp

int binarySearch(int a[], int l, int r, int x) // recursive
{
   if (r >= l) 
   {
        int mid = l + (r - l)/2;
 
        // If the element is present at the middle itself
        
        if (a[mid] == x)  
            return mid; // return the index
 
        // If element is smaller than mid, then 
        // it can only be present in left subarray
        if (a[mid] > x) 
            return binarySearch(a, l, mid-1, x);
 
        // Else the element can only be present
        // in right subarray
        return binarySearch(a, mid+1, r, x);
   }
 

   return -1;
}