Question

我尝试从数据文件中读取值。但是，每列需要提取的值不同。

值列表如下所示：

8
11
0        0   -50
1000     0   -50
2000     0     0
0      500     0
500    500     0
0     1000   -50
1000  1000     0
2000  1000   150

使用下面的代码，我可以将所有值存储在数组中，但我想分别存储8和11。此外，第一列（0到2000）应存储在一个阵列中，第二列（0到1000）存储在第二个阵列中，第三列（-50到150）存储在第三个阵列中。

#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    cout << "PROGRAM PIPE NETWORK" << endl;

    //Read input data file
    int n;
    double *array;

    cout << "How many data sets do you have?\nDatasets: ";
    cin >> n;

    ifstream infile("pipedata.dat");
    array = new double[n];

    for (int i = 1; i < n; ++i)
        infile >> array[i];

    return 0;
}

我希望你们中的一些人可以帮助我，请尽量不写一般答案。我在这个话题中很安静。问候。

编辑1：

另一种尝试如下，但它有时会起作用，但我也会遇到数据地址或堆困难的错误。有时它可以工作，但大部分时间我的程序都停止工作。

int main()
{
cout << "PROGRAM PIPE NETWORK" << endl;

// Read input all data files
int n; double *input;
int limit_x, x; double *array_x;
int limit_y, y; double *array_y;
int limit_q, q; double *array_q;
int n_nodes, n_tubes;

cout << "How many data sets do you have?\nDatasets: ";
cin >> n;

ifstream infile("pipedata.dat");
input = new double[n];
for (int i = 0; i<n; ++i) infile >> input[i];

// Assign input values to their variables
// Number of nodes and number of tubes
n_nodes = input[0];
n_tubes = input[1];

cout << "Input values" << endl;
for (int i = 0; i < n; ++i)
{
    cout << input[i] << endl;
}
cout << "---------------------------------------" << endl;
cout << "X-Values" << endl;
// Node data x-values
x = n_nodes;
limit_x = n_nodes * 3;
array_x = new double[x];
for (int i = 0; i < limit_x; i += 3)    array_x[i] = 0;
for (int i = 0; i < limit_x; i+=3)      array_x[i] = input[i+2];

for (int i = 0; i < limit_x; i+=3)      cout << array_x[i] << endl;
return 0;
}

一切正常，＆＃34;输入＆＃34;但不是array_x。另外，我想和其他5个变量做同样的事情。我知道这不是最好的解决方案，但我真的不明白为什么它不起作用。

Answer 1

我不知道并发症是什么，但这是一个例子：

std::vector<int> array_1;
std::vector<int> left;
std::vector<int> middle;
std::vector<int> right;
int temp;

// Read two numbers into an array
data_file >> temp;
array_1.push_back(temp);
data_file >> temp;
array_1.push_back(temp);

// Read columns of data into separate arrays
int left_value, middle_value, right_value;
while (data_file >> left >> middle >> right)
{
  left.push_back(left_value);
  middle.push_back(middle_value);
  right.push_back(right_value);
}

以上是许多例子。它没有优化。

另一个示例使用std::getline和std::istringstream，这样可以更好地符合行的对齐方式。

编辑1：逐行处理

std::string text_line;
std::istringstream parser;

// Read a line from the file
std::getline(data_file, text_line);

// Extract the numbers from the line:
parser.str(text_line); // Initialize the std::istringstream with the text line.
int value_1 = 0;
parser >> value_1; // Extract the first number of the first line.

// Read the second line from the file
std::getline(data_file, text_line);

// Extract the numbers from the line:
parser.str(text_line); // Initialize the std::istringstream with the text line.
int value_2 = 0;
parser >> value_2; // Extract the first number of the second line.

// After reading 2 lines, the file pointer should be pointing
//   at the 3rd line.
// The data format changes at the 3rd line with 3 numbers per line.
// Let's use an array this time, one per column.
const unsigned int  ARRAY_CAPACITY = 256;
int column_1[ARRAY_CAPACITY];
int column_2[ARRAY_CAPACITY];
int column_3[ARRAY_CAPACITY];
unsigned int row = 0;

// Read until the data stream fails, usually at EOF.
while (std::getline(data_file, text_line))
{

  // ** Very important, check for overflow before using array**
  if (row >= ARRAY_CAPACITY)
  {
     // Either reallocate and copy old array or ...
     // Crash the program.
     std::cerr << "Array capacity is too small.\n";
     exit(1);
  }

  // Initialize the parser
  parser.str(text_line);

  // Extract the first value and place into array, directly.
  parser >> column_1[row];  

  // Likewise, the next columns.
  parser >> column_2[row];
  parser >> column_3[row];

  // Advance the column index to the next row (line)
  ++row;
}

从每列具有不同数值的文件中读取值，C ++

1 个答案: