将文件中的数据存储到数组中

storing data from a file into an array

本文关键字：数组 存储 文件 数据      更新时间：2023-10-16

我编写了以下代码来读取列中的数据从文件(area.inp(到数组。 在屏幕中显示数据时，第一个"for"循环显示正确的数字(因此代码正确读取文件中的数字(，但第二个"for"循环显示不正确的数字集。我无法解决这个问题。 我将不胜感激有关该问题的任何指导。

area.inp

001.000    003.000
002.000    004.000
006.000    005.000
004.000    002.000
002.000    001.000

法典

#include <iostream>
#include <iomanip>
#include <fstream>
#include <algorithm>
#include <iterator>

using namespace std;

int main(int argc, char **argv)
{
    int j=0;
    double X[j];
    double Y[j];
    static double *p;
    double *q;
    p=X;
    q=Y;

//**** Counting the number of lines
    ifstream myfile("area.inp");
    myfile.unsetf(ios_base::skipws);
    int points = count(
        istream_iterator<char>(myfile),
        istream_iterator<char>(),
        'n');
    cout << "Number of data in file: " << points << "n";
//****  Open data file and result
    cout <<"file is open"<< endl;
    ifstream infile;
    infile.open("area.inp", ios::in);

    cout <<"Reading data from file"<< endl; 
    for (j=0; j<points; j++)
        {
            cout << std::setprecision(3) << std::fixed;;
            infile >> X[j] >> Y[j];
            cout << "Value of X["<<j<<"]: " << X[j] << endl;
            cout << "Value of Y["<<j<<"]: " << Y[j] << endl;
        }
    cout <<"Showing numbers stored in array"<< endl;

            for (j=0; j<points; j++)
            {
                cout << "Value of X["<<j<<"]: " << X[j] << endl;
                cout << "Value of Y["<<j<<"]: " << Y[j] << endl;
            }
    infile.close();
    return 0;
}
Number of data in file: 5
file is open
Reading data from file
Value of X[0]: 1.000
Value of Y[0]: 3.000
Value of X[1]: 2.000
Value of Y[1]: 4.000
Value of X[2]: 6.000
Value of Y[2]: 5.000
Value of X[3]: 4.000
Value of Y[3]: 2.000
Value of X[4]: 2.000
Value of Y[4]: 2.000
Showing numbers stored in array
Value of X[0]: 5.000
Value of Y[0]: 3.000
Value of X[1]: 2.000
Value of Y[1]: 4.000
Value of X[2]: 4.000
Value of Y[2]: 5.000
Value of X[3]: 4.000
Value of Y[3]: 2.000
Value of X[4]: 2.000
Value of Y[4]: 2.000

------------------
(program exited with code: 0)
Press return to continue

如注释中所述，您正在创建一个 0 长度的数组。要按照自己的方式做事，您必须在计算文件中的点数后分配带有new的数组：

double *X = new double[points];
double *Y = new double[points];

然后在程序结束时，用delete释放内存。

我建议您避免使用数组，而是使用 std::vector .在示例中，我使用 std::pair 来存储点，但您可以更改它。

// Using a vector of pairs
std::vector<std::pair<double, double>> data;
ifstream infile;
infile.open("area.inp");
// You should check here to make sure the file opened ok
// Read the file. No need to know size ahead of time
std::pair<double, double> tmp;
while (infile >> tmp.first >> tmp.second) {
    data.push_back(tmp);
}
// Print the results
std::cout << "Number of pairs: " << data.size() << std::endl;
for (auto p : data) {
    std::cout << p.first << ", " << p.second << std::endl;
}
数组

X[] 和 Y[] 的大小为零。好奇为什么没有赛格故障

尝试更改如下，

#include <iostream>
#include <iomanip>
#include <fstream>
#include <algorithm>
#include <iterator>

using namespace std;

int main(int argc, char **argv)
{
int j=0;
static double *p;
double *q;

//**** Counting the number of lines
ifstream myfile("area.inp");
myfile.unsetf(ios_base::skipws);
const int points = count(
    istream_iterator<char>(myfile),
    istream_iterator<char>(),
    'n');
double X[points];
double Y[points];
p=X;
q=Y;
cout << "Number of data in file: " << points << "n";
//****  Open data file and result
cout <<"file is open"<< endl;
ifstream infile;
infile.open("area.inp", ios::in);

cout <<"Reading data from file"<< endl; 
for (j=0; j<points; j++)
    {
        cout << std::setprecision(3) << std::fixed;;
        infile >> X[j] >> Y[j];
        cout << "Value of X["<<j<<"]: " << X[j] << endl;
        cout << "Value of Y["<<j<<"]: " << Y[j] << endl;
    }
cout <<"Showing numbers stored in array"<< endl;

        for (j=0; j<points; j++)
        {
            cout << "Value of X["<<j<<"]: " << X[j] << endl;
            cout << "Value of Y["<<j<<"]: " << Y[j] << endl;
        }
infile.close();
return 0;
}
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