在c ++中，计算结果为零[关闭]

Question

我正在编写此代码，在其中计算一个人从地球到达特定星球所花费的时间。我的问题是，对于时间变量，我一直保持为零。结果，其他变量小时和年也给出零。怎么了？

我知道这不是强制转换，因为它们已经加倍了。

#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;

int main()
{
    char choice = 0;
    double weight = 0;
    double speed = 0;
    double time = 0;
    double newWeight;
    double distance = 0;
    double gravity = 0;
    double newtoSun = 0;
    double earthtoSun = 93;
    double days = 0;
    double years = 0;
    string planet;

    cout << "welcome" << endl;
    cout << "menu" << endl;
    cout << "a) mercury" << endl;
    cout << "b)Venus" << endl;
    cin >> choice;

    if (choice >= 'a' && choice <= 'd')
    {
        cout << "enter weight" << endl;
        cin >> weight;

        cout << "What speed u want?" << endl;
        cin >> speed;

        if (choice == 'a')
        {
            newtoSun = 36;
            gravity = 0.27;
            planet = "Mercury";
        }
        else if (choice == 'b')
        {
            newtoSun = 67;
            gravity = 0.86;
            planet = "Venus";
        }
        else if (choice == 'c')
        {
            newtoSun = 93;
            gravity = 1;
            planet = "Earth";
        }
        else if (choice == 'd')
        {
            newtoSun = 141;
            gravity = 0.37;
            planet = "Mars";
        }

        newWeight = weight * gravity;
        time = distance / speed;
        distance = abs(earthtoSun - newtoSun);
        days = time / 24;
        years = days / 365;

        cout << "INTERPLANETARY TRAVEL: Earth to " << choice << endl;
        cout << "-------------------------------------------" << endl;
        cout << "Your weight on " << planet << fixed << setw(5)
                << setprecision(2) << newWeight << endl;
        cout << distance << endl;
        cout << speed << endl;
        cout << "Your travel time to " << planet << ":" << endl;
        cout << "In Hours: " << setw(2) << time << "hours" << endl;
        cout << "In Days : " << setw(2) << days << "days" << endl;
        cout << "In Years  : " << setw(2) << years << "years" << endl << endl;

    }

    else if (choice == 'q')
    {
        cout << "You quit" << endl;
    }

    else
        cout << "You have entered an invalid selection" << endl;

    return 0;
}

Answer 1

time = distance / speed;
distance = abs(earthtoSun - newtoSun);

这些语句是向后的。