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Binary Search in C++ using Standard Template Library (STL) function binary_search()

In this article, we are going to learn how to search an element from an array using binary_search() function of C++ Standard Template Library (STL)?
Submitted by IncludeHelp, on January 04, 2018

Given an array and we have to search an element using binary_search(), which is a function of algorithm header of C++ Standard Template Library.

binary_search() function

It is a built-in function, which is used to search an element from an array using Binary Search Algorithm.

Syntax:

binary_search(start_address, end_address, element_to_search);

Here,

1. start_address - starting array element’s pointer
2. end_address - ending array element’s pointer
3. element_to_search - element to search

Steps:

1. Declare and define an array
2. Sort the array (here, we are using sort() function to sort array in ascending order).
3. Find the element using binary_search() function.
4. Print the message with its index if it exists.

Program to implement Binary Search using C++ STL

#include <iostream>
#include <algorithm>

using namespace std;
 
//function to display array list
void dispArray(int arr[], int size)
{
    for(int i = 0; i < size; i++)
        cout <<" "<< arr[i];
    cout<<endl;
}
 

//main code for binary search 
int main()
{
    int a[]= {10, 1, 20, 2, 30, 4};
    
    //get array length
    int arr_length = sizeof(a) / sizeof(int);
    
    //print array
    cout<<"Array elements are: ";
    dispArray(a, arr_length);
 
    //sort the array
    sort(a, a + arr_length);
    cout<<"Sorted array elements: ";
    dispArray(a, arr_length);
    
    //searching 30 in the array
    if(binary_search(a, a+ arr_length, 30))
        cout<<"Element found"<<endl;
    else
        cout<<"Element does not found"<<endl;
        
    return 0;
}

Output

Array elements are:  10 1 20 2 30 4
Sorted array elements:  1 2 4 10 20 30
Element found