Question

我想知道是否有人可以帮我解决我的问题。所以我正在研究的程序试图计算非停靠航班的飞行距离，而不是在所需目的地以外的一个城市停靠的航班。到目前为止，我已经获得了前两个数据集，但是当我尝试获取第三个数据集时，我得到了第二组城市。我正在使用void函数，这是我的第一个带void函数的程序。我从中获取日期的部分的代码是：

#include <fstream>
#include <iostream>
#include <string>

using namespace std;
void readFile(int choice, double &begLat, double &begLon, string &begCity,
    double &midLat, double &midLon, string &midCity,
    double &endLat, double &endLon, string &endCity);
void intro();
void askDataSet(int &selection);
int dist(double lat1, double lon1, double lat2, double lon2);

//--------------------------------------------------

int main()
{

    intro();

    double begLat, begLon, midLat, midLon, endLat, endLon;
    string begCity, midCity, endCity;
    int choice;
    askDataSet(choice);

    readFile(choice, begLat, begLon, begCity, midLat, midLon, midCity, endLat, endLon, endCity);
    cout << "The First City at coordinates " << begLat << " and " << begLon << " is:  " << begCity << endl;
    cout << "The Second City at coordinates " << midLat << " and " << midLon << " is:  " << midCity << endl;
    cout << "The Third City at coordinates " << endLat << " and " << endLon << " is:  " << endCity << endl;

    int leg1, leg2, nonstop;
    leg1 = dist(begLat, begLon, midLat, midLon);
    leg2 = dist(midLat, midLon, endLat, endLon);
    nonstop = dist(begLat, begLon, endLat, endLon);
    cout << "The legs are " << leg1 << " and " << leg2 << endl;
    cout << "Nonstop is " << nonstop << endl;

    cout << "It is " << leg2 + leg1 - nonstop << " fewer miles for non-stop" << endl;

    system("pause");
    return 0;
}

void readFile(int choice, double &begLat, double &begLon, string &begCity,
    double &midLat, double &midLon, string &midCity,
    double &endLat, double &endLon, string &endCity)
{
    ifstream dataIn;
    dataIn.open("cities.txt");
    if (dataIn.fail())
    {
        cout << "Error.  File does not exist. " << endl;
        exit(1);
    }
    if (choice == 1)
    {
        dataIn >> begLat;
        dataIn >> begLon;
        dataIn.get();
        getline(dataIn, begCity);
        dataIn >> midLat;
        dataIn >> midLon;
        dataIn.get();
        getline(dataIn, midCity);
        dataIn >> endLat;
        dataIn >> endLon;
        dataIn.get();
        getline(dataIn, endCity);
    }

    string trash;
    if (choice == 2)
    {
        getline(dataIn, trash);
        getline(dataIn, trash);
        getline(dataIn, trash);
        getline(dataIn, trash);
        getline(dataIn, trash);
        getline(dataIn, trash);
        getline(dataIn, trash);

        dataIn >> begLat;
        dataIn >> begLon;
        dataIn.get();
        getline(dataIn, begCity);
        dataIn >> midLat;
        dataIn >> midLon;
        dataIn.get();
        getline(dataIn, midCity);
        dataIn >> endLat;
        dataIn >> endLon;
        dataIn.get();
        getline(dataIn, endCity);
    }


    if (choice == 3)
    {
        getline(dataIn, trash);
        getline(dataIn, trash);
        getline(dataIn, trash);
        getline(dataIn, trash);
        getline(dataIn, trash);
        getline(dataIn, trash);
        getline(dataIn, trash);

        dataIn >> begLat;
        dataIn >> begLon;
        dataIn.get();
        getline(dataIn, begCity);
        dataIn >> midLat;
        dataIn >> midLon;
        dataIn.get();
        getline(dataIn, midCity);
        dataIn >> endLat;
        dataIn >> endLon;
        dataIn.get();
        getline(dataIn, endCity);

    }
}

void intro()
{
    cout << "In this lab we will try to figure out how much shorter it is to fly non-stop compared to one-stop." << endl;
    cout << endl;
}

void askDataSet(int &selection)
{
    cout << "Do you wish to use dataset 1, 2, or 3? ";
    cin >> selection;
    while (selection < 1 || selection > 3)
    {
        cout << "The only valid choices are 1-3. Please re-enter";
        cin >> selection;
        cout << endl;
    }
}

int dist(double lat1, double lon1, double lat2, double lon2)
{
    double diffLat, diffLon, hyp;
    diffLat = (lat1 - lat2) * 69;
    diffLon = (lon1 - lon2) * 53;
    hyp = sqrt(diffLat * diffLat + diffLon * diffLon);
    return static_cast<int>(hyp);
}

Answer 1

我认为你正在阅读＃3中的选择，就像阅读选择＃2一样。所以基本上你正在阅读相同的数据集。在选择＃3中，您需要在实际读取数据之前跳过更多数据行。所以根据你的方法（看起来有点天真），应该有两倍的getline（dataIn，trash）;如选择＃2。

从单独的文本文件中获取数据集

1 个答案: