binary search stl in c++

// C++ code to demonstrate the working of binary_search() 
  
#include<bits/stdc++.h>  
using namespace std; 
  
int main() 
{ 
    // initializing vector of integers 
    vector<int> arr = {10, 15, 20, 25, 30, 35}; 
      
    // using binary_search to check if 15 exists 
    if (binary_search(arr.begin(), arr.end(), 15)) 
       cout << "15 exists in vector"; 
    else 
       cout << "15 does not exist"; 
       
    cout << endl; 
      
    // using binary_search to check if 23 exists 
    if (binary_search(arr.begin(), arr.end(), 23)) 
         cout << "23 exists in vector"; 
    else 
         cout << "23 does not exist"; 
       
    cout << endl;     
} 

#include<iostream> 
using namespace std; 
int binarySearch(int arr[], int p, int r, int num) { 
   if (p <= r) { 
      int mid = (p + r)/2; 
      if (arr[mid] == num)   
         return mid ; 
      if (arr[mid] > num)  
         return binarySearch(arr, p, mid-1, num);            
      if (arr[mid] < num)
         return binarySearch(arr, mid+1, r, num); 
   } 
   return -1; 
} 
int main(void) { 
   int arr[] = {1, 3, 7, 15, 18, 20, 25, 33, 36, 40}; 
   int n = sizeof(arr)/ sizeof(arr[0]); 
   int num = 33; 
   int index = binarySearch (arr, 0, n-1, num); 
   if(index == -1)
      cout<< num <<" is not present in the array";
   else
      cout<< num <<" is present at index "<< index <<" in the array"; 
   return 0; 
}

binary_search(startaddress, endaddress, valuetofind)

startaddress: the address of the first element of the array.
endaddress: the address of the last element of the array.
valuetofind: the target value which we have to search for.

int result = -1;
  int low = 0;
  int high = N-1; // N - # of elements
   while (low <= high)
   {  mid = (low + high) / 2;
      if ( item == vector[mid])
	  {  result = mid;
	     break; 
      }
      else if (item > vector[mid] )
	           { low =  mid + 1; }
          else  { high = mid - 1; }
   }