Question

我正在尝试读取格式为的文本文件：

5
1.00   0.00
0.75   0.25
0.50   0.50
0.25   0.75
0.00   1.00

代码是：

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

int totalDataPoints; // this should be the first line of textfile i.e. 5
std::vector<double> xCoord(0); //starts from 2nd line, first col
std::vector<double> yCoord(0); //starts from 2nd line, second col
double tmp1, tmp2;

int main(int argc, char **argv)
{
    std::fstream inFile;

    inFile.open("file.txt", std::ios::in);

    if (inFile.fail()) {
        std::cout << "Could not open file" << std::endl;
        return(0);
    } 

    int count = 0;

     while (!inFile.eof()) { 
         inFile >> tmp1;
         xCoord.push_back(tmp1);
         inFile >> tmp2;
         yCoord.push_back(tmp2);
         count++;
     }

     for (int i = 0; i < totalDataPoints; ++i) {
         std::cout << xCoord[i] << "    " << yCoord[i] << std::endl;
     }
    return 0;
}

我没有得到结果。我的最终目标是将其作为函数，并将x，y值称为类的对象。

Answer 1

int totalDataPoints;是一个全局变量，因为你没有用值初始化它，所以它将被初始化为0。然后在你的for循环中

for (int i = 0; i < totalDataPoints; ++i) {
     std::cout << xCoord[i] << "    " << yCoord[i] << std::endl;
}

由于i < totalDataPoints（0 < 0）为false，您将执行任何操作。我怀疑你打算使用

for (int i = 0; i < count; ++i) {
     std::cout << xCoord[i] << "    " << yCoord[i] << std::endl;
}

或者

totalDataPoints = count;

在for循环之前。

我还建议您不要使用while (!inFile.eof())来控制文件的读取。修复它您可以使用

 while (inFile >> tmp1 && inFile >> tmp2) { 
     xCoord.push_back(tmp1);
     yCoord.push_back(tmp2);
     count++;
 }

这将确保循环仅在有数据要读取时运行。有关详细信息，请参阅：Why is “while ( !feof (file) )” always wrong?

Answer 2

只需在代码中进行简单的更改即可。您无法从第一行的totalDataPoints获取file.txt。然后你走完每条线直到最后。

int count = 0;

    inFile>>totalDataPoints;

     while (!inFile.eof()) {
         inFile >> tmp1;
         xCoord.push_back(tmp1);
         inFile >> tmp2;
         yCoord.push_back(tmp2);
         count++;
     }

通过 for循环，你可以这样做，这里int count = 0是不必要的：

inFile>>totalDataPoints;

    for (int i=0; i<totalDataPoints; i++)
    {
        inFile >> tmp1;
         xCoord.push_back(tmp1);
         inFile >> tmp2;
         yCoord.push_back(tmp2);
    }

从制表符分隔文件中读取2D数据并存储在矢量C ++中

2 个答案: