将数据文件读入2d数组c ++ [英] reading data file into 2d array c++

问题描述

我有一个有2列和许多行的文本文件。每列由空格分隔。我需要读它们到二维数组进一步计算。
我的数据文件看起来像

I have a text file with 2 columns and many rows. each column is separated by spaces. i need to read them to a 2D array for further calculations. my data file looks like

0.5 0.479425539
1   0.841470985
1.5 0.997494987
2   0.909297427
2.5 0.598472144
3   0.141120008
3.5 -0.350783228
4   -0.756802495
4.5 -0.977530118
5   -0.958924275  

我的微弱尝试是

#include <iostream>
#include <fstream>
#include <string>
#include <conio.h>
#include <ctype.h>
using namespace std;

int main () {
  char line,element;
  std::ifstream myfile ("C:\\Users\\g\\Desktop\\test.txt");
  if (myfile.is_open())
  {
    while ( myfile.good() )
    {
      getline(myfile,line);
       cout << line<<endl;               
      _getch();
    }
    myfile.close();

  }

  else cout << "Unable to open file"; 

  return 0;

}

问题是我无法正确读取....它读取整行...如果我将分隔符指定为'space'，那么它不读取下一行。

The problem is I'm not able to read them correctly.... its either reading the whole line... if I specify the delimiter as 'space' then, its not reading the next row.

错误。和我应该做什么将数据存储到2d阵列进一步计算。
谢谢

Pls point out whats wrong. and what should i do to store the data into 2d array for further calculations. Thank you

推荐答案

您可以将整行读入 std :: string ，然后使用 std :: istringstream 从该行中提取值。

You can read the whole line into a std::string, then use std::istringstream to extract the values from the line.

一个完整的工作程序：

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

int main()
{
    std::ifstream file("C:\\Users\\g\\Desktop\\test.txt");

    std::string line;

    // Read a line of input from the file
    while (std::getline(file, line))
    {
        // `istringstream` behaves like a normal input stream
        // but can be initialized from a string
        std::istringstream iss(line);

        float value;

        // The input operator `>>` returns the stream
        // And streams can be used as a boolean value
        // A stream is "true" as long as everything is okay
        while (iss >> value)
        {
            std::cout << "Value = " << value << '\t';
        }

        // Flush the standard output stream and print a newline
        std::cout << std::endl;
    }
}

给定文件中的内容，前三行输出应为：

Given the contents in the file being as in the question, the first three lines of output should be:

Value = 0.5 Value = 0.479425539
Value = 1   Value = 0.841470985
Value = 1.5 Value = 0.997494987

---

对于2d阵列， std :: vector of std :: array ：

#include <vector>
#include <array>

...

std::vector<std::array<float, 2>> array;

...

float value1, value2;
if (iss >> value1 >> value2)
{
    std::cout << "Values = " << value1 << ", " << value2;

    array.emplace_back(std::array<int, 2>{{value1, value2}});
}

现在第一行的值是 array [0] [0] 和 array [0] [1] ，最后一行的值是 array [array.size ） - 1] [0] 和 array [array.size（） - 1] [1] 。

Now the first line values are array[0][0] and array[0][1], and the last lines values are array[array.size() - 1][0] and array[array.size() - 1][1].

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