5.1.7.1 Binary searching

#include <iostream>
#include <vector>
#include <algorithm>
#include <iterator>
#include <ctype.h>
#include <string>

using namespace std;

struct Country
{
    string name;
    int area;
Country(string n,int a):name(n),area(a){}

};
void print(const Country & v)
{
    cout<<v.area<<" ";
}


void printMessage(bool value)
{
    if (value)
    {
        cout<<"Found!\n";
    }
    else
    {
        cout<<"Not found!\n";
    }
}
bool ascending_one_key(const Country& a,const Country& b)
{
    return a.area < b.area;
}

int main()
{
    vector <Country> countries = {
            {"India", 3287 },{ "Argentina", 2780 },
            {"Brazil", 8515}, {"Australia", 7692},
            {"China", 9572 },{ "United States of America", 9525 },
            {"Russia", 17098 },{ "Canada", 9984 },
            {"Kazakhstan", 	2724 }, {"Algeria", 2381 }
    };

    int area ;

    cin >> area;

    Country b("",area);

    sort(countries.begin(), countries.end(),ascending_one_key);

    printMessage(binary_search(countries.begin(), countries.end(), b,ascending_one_key));

    return 0;
}