c++循环的作业

#include <iostream>
using namespace std;

int main( void )
{
    unsigned sum = 0;

    unsigned i=0;
    while( i<=100 )
    {
        if( i%2 == 0 )
            sum += i;
        ++i;
    }
    cout << sum << endl;
}

#include <iostream>
#include <string>
using namespace std;

int main( void )
{
    const char* correct_user = "guess";
    const char* correct_pswd = "password";

    string user, pswd;
    do
    {
        cout << "用户: ";
        getline( cin, user );
        cout << "密码: ";
        getline( cin, pswd );
    }
    while( user!=correct_user || pswd!=correct_pswd );

    cout << "登陆成功" << endl;
}

#include <iostream>
using namespace std;

int main( void )
{
    unsigned sum = 0;
    for( unsigned i=0; i<=100; i+=2 )
        sum += i;
    cout << sum << endl;
}