cin输入的问题

#include <iostream>

int main(int argc,constchar * argv[]) {

    // insert code here...

    

    longlong population_us,population_world;

    

    std::cout <<"Enter the world's population : " ;

    std::cin >> population_world;

    std::cout <<"Enter the population of the US : " ;

    std::cin >> population_us;

    std::cout <<"The population of the US is " <<double(population_us) / double(population_world) *100 <<"% of the world population" <<std::endl;

    std::cout <<310783781.0/6898758899.0 <<std::endl;

    

    return0;

}

输入的时候：

Enter the world's population : 6898758899

Enter the population of the US : 310783781

The population of the US is 4.50492% of the world population

0.0450492

Program ended with exit code: 0

非正常输入：

Enter the world's population : 6898758899.0

Enter the population of the US : The population of the US is 0% of the world population

0.0450492

Program ended with exit code: 0

侥幸通过输入：

Enter the world's population : 6898758899

Enter the population of the US : 310783781.0

The population of the US is 4.50492% of the world population

0.0450492

Program ended with exit code: 0

问题疑问：

1.cin操作机制

2.如何去操作避免这种误输入

========================华丽的分割线，就是那么英俊========================

补充：

#include <iostream>

int main(int argc,const char * argv[]) {

    // insert code here...

    

    usingnamespace std;

    constint ArSize = 20;

    char name[ArSize];

    char dessert[ArSize];

    

    cout <<"Enter your name:\n";

    cin.getline(name, ArSize);

    cout <<"Enter your favorite dessert:\n";

    cin.getline(dessert, ArSize);

    cout <<"I have some delicious " << dessert;

    cout <<" for you, " << name << ".\n";

    

    return0;

}

正常输入：

Enter your name:

Dirk Hammernose

Enter your favorite dessert:

Radish Torte

I have some delicious Radish Torte for you, Dirk Hammernose.

Program ended with exit code: 0

非正常输入：

当我将ArSize 改成10的时候，name无法容纳那么多字符，出现问题

Enter your name:

Dirk Hammernose

Enter your favorite dessert:

I have some delicious  for you, Dirk Hamm.

Program ended with exit code: 0

========================华丽的分割线，就是那么英俊========================

int main(int argc, const char * argv[]) {

    // insert code here...

    

    using namespace std;

    const int ArSize = 10;

    char name[ArSize];

    char dessert[ArSize];

    

    cout << "Enter your name:\n";

    cin.get(name, ArSize).get();

    cout << "Enter your favorite dessert:\n";

    cin.get(dessert, ArSize).get();

    cout << "I hace some delicious " << dessert;

    cout << " for you, " << name << ".\n";

    

    return 0;

}

非正常输入：

Enter your name:

Mai Parfait

Enter your favorite dessert:

I hace some delicious tfor you, Mai Parfa.

Program ended with exit code: 0