C ++将数据从文本文件读取到结构数组中

Question

我对 C++ 编程相当陌生，并且在将文本文件中的数据读取到结构数组中时遇到了一些麻烦。我查看了类似的帖子以尝试找到解决方案，但是，我无法使它对我有用，并想寻求一些帮助。以下是我的数据集示例（P.S. 我将使用多个不同大小的数据集）：

00010 0
00011 1
00100 0
00101 1
00110 1
00111 0
01000 0
01001 1

下面是我的代码：

int variables = 5;

typedef struct {
    int variables[variables];
    int classification;
} myData;

//Get the number of rows in the file
int readData(string dataset)
{
    int numLines = 0;
    string line;
    ifstream dataFile(dataset);
    while (getline(dataFile, line))
    {
        ++numLines;
    }
    return numLines;
}

//Store data set into array of data structure
int storeData(string dataset)
{
    int numLines = readData(dataset);

    myData *dataArray = new myData[numLines];

    ...

    return 0;
}

int main()
{
    storeData("dataset.txt");

我想要实现的是将文本文件每行的前 5 个整数存储到“myData”结构中的“变量”数组中，然后将最后一个以空格分隔的整数存储到“分类”中变量，然后将该结构存储到数组“dataArray”中，然后移至下一行。

例如，数组中的第一个结构将包含变量 [00010]，分类为 0。第二个结构将包含变量 [00011]，分类为 1，依此类推。

非常感谢您对此的帮助，干杯！

Answer 1

为您的类型提供流提取和流插入运算符：

#include <cstddef>    // std::size_t
#include <cstdlib>    // EXIT_FAILURE
#include <cctype>     // std::isspace(), std::isdigit()
#include <vector>     // std::vector<>
#include <iterator>   // std::istream_iterator<>, std::ostream_iterator<>
#include <fstream>    // std::ifstream
#include <iostream>   // std::cout, std::cerr, std::cin
#include <algorithm>  // std::copy()

constexpr std::size_t size{ 5 };

struct Data {
    int variables[size];
    int classification;
};

// stream extraction operator
std::istream& operator>>(std::istream &is, Data &data)
{
    Data temp;  // don't write directly to data since extraction might fail
               //  at any point which would leave data in an undefined state.

    int ch;  // signed integer because std::istream::peek() and ...get() return
            //  EOF when they encounter the end of the file which is usually -1.

                                                    // don't feed std::isspace
                                                   //  signed values
    while ((ch = is.peek()) != EOF && std::isspace(static_cast<unsigned>(ch)))
        is.get();  // read and discard whitespace

             // as long as
            //              +- we didn't read all variables
           //               |         +-- the input stream is in good state
          //                |         |      +-- and the character read is not EOF
         //                 |         |      |   
    for (std::size_t i{}; i < size && is && (ch = is.get()) != EOF; ++i)
        if (std::isdigit(static_cast<unsigned>(ch)))
            temp.variables[i] = ch - '0';  // if it is a digit, assign it to our temp
        else is.setstate(std::ios_base::failbit);  // else set the stream to a 
                                                  // failed state which will 
                                                 // cause the loop to end (is)

    if (!(is >> temp.classification))  // if extraction of the integer following the
        return is;                    // variables fails, exit.

    data = temp;  // everything fine, assign temp to data
    return is;
}

// stream insertion operator
std::ostream& operator<<(std::ostream &os, Data const &data)
{
    std::copy(std::begin(data.variables), std::end(data.variables),
              std::ostream_iterator<int>{ os });
    os << ' ' << data.classification;
    return os;

}

int main()
{
    char const *filename{ "test.txt" };
    std::ifstream is{ filename };

    if (!is.is_open()) {
        std::cerr << "Failed to open \"" << filename << "\" for reading :(\n\n";
        return EXIT_FAILURE;
    }

    // read from ifstream
    std::vector<Data> my_data{ std::istream_iterator<Data>{ is },
                               std::istream_iterator<Data>{} };

    // print to ostream
    std::copy(my_data.begin(), my_data.end(),
              std::ostream_iterator<Data>{ std::cout, "\n" });
}

---

未注释它看起来不那么可怕：

std::istream& operator>>(std::istream &is, Data &data)
{
    Data temp;
    int ch;

    while ((ch = is.peek()) != EOF && std::isspace(static_cast<unsigned>(ch)))
        is.get();

    for (std::size_t i{}; i < size && is && (ch = is.get()) != EOF; ++i)
        if (std::isdigit(static_cast<unsigned>(ch)))
            temp.variables[i] = ch - '0';
        else is.setstate(std::ios_base::failbit);

    if (!(is >> temp.classification))
        return is;

    data = temp;
    return is;
}

std::ostream& operator<<(std::ostream &os, Data const &data)
{
    std::copy(std::begin(data.variables), std::end(data.variables),
              std::ostream_iterator<int>{ os });
    os << ' ' << data.classification;
    return os;

}

Answer 2

看起来你正试图将二进制值保留为整数索引。如果是这种情况，它将在内部转换为整数。您可能需要再次将 int 转换为二进制。

如果您想保留文本文件中的数据，那么您需要为索引值选择 char/string 类型。对于分类，它的值似乎是 0 或 1。因此您可以选择 bool 作为数据类型。

#include <iostream>
#include <map>

using namespace std;

std::map<string, bool> myData;

int main()
{
    // THIS IS SAMPLE INSERT. INTRODUCE LOOP FOR INSERT.
    /*00010 0
    00011 1
    00100 0
    00101 1
    00110 1*/
    myData.insert(std::pair<string, bool>("00010", 0));
    myData.insert(std::pair<string, bool>("00011", 1));
    myData.insert(std::pair<string, bool>("00100", 0));
    myData.insert(std::pair<string, bool>("00101", 1));
    myData.insert(std::pair<string, bool>("00110", 1));

    // Display contents
    std::cout << "My Data:\n";
    std::map<string, bool>::iterator it;

    for (it=myData.begin(); it!=myData.end(); ++it)
        std::cout << it->first << " => " << it->second << '\n';

    return 0;
}