从 txt 文件中分离并行数组

Question

我是一个非常新手的程序员，我正在尝试编写一个程序来读取一个 txt 文件，其中包含 5 名学生的姓名（仅限名字）以及每个学生的四项考试成绩。我试图将名字读入一个名为 students 的数组，然后将分数读入 4 个单独的数组，分别命名为 test1、test2、test3、test4，然后从监视器上显示它。该文件如下所示：

Steve 78 65 82 73

Shawn 87 90 79 82

Annie 92 90 89 96

Carol 72 65 65 60

Kathy 34 50 45 20

我很难分解和组织数组。有人能帮我吗？请记住我是新手，所以我对编程了解不多。

到目前为止，这是我的代码：

#include <cstdlib>
#include <iostream>
#include <string>
#include <fstream>
#include <iomanip>
#include <ctime>
#define over2 "\t\t"
#define over3 "\t\t\t"
#define over4 "\t\t\t\t"
#define down5 "\n\n\n\n\n"


using namespace std;



int main(int argc, char *argv[])
{

    
    ifstream inputFile;
    
    
    //Constant for max string size
    const int SIZE = 5;
     

    //Constant for the scores
    string names[SIZE], fileName, line, test1[SIZE], test2[SIZE], test3[SIZE], test4[SIZE];


    //input section, user enters their file name
    cout << down5 << down5 << over2 << "Please enter your file name: ";
    cin >> fileName;
    system("CLS");
    

    

    //open the file containing the responses
    inputFile.open(fileName.c_str());
     cout << endl;

    //kicks you out if file isn't found
    if (inputFile)
    {
        for(int i = 0; i < SIZE; i++)
        {  
           getline(inputFile, line);
            names[i] = line;
            getline(inputFile, line);
            test1[i] = line;
            getline(inputFile, line);
            test2[i] = line;
            getline(inputFile, line);
            test3[i] = line;
            getline(inputFile, line);
            test4[i] = line;
        }   
            inputFile.close();  
    }
    cout << down5 << over3 << "Student\tTest1\tTest2\tTest3\tTest4\n";
    cout << over3 << "-------\t-----\t-----\t-----\t-----\n";   
    for(int i = 0; i < SIZE; i++)
    {
        cout << over3 << names[i] << endl;
        cout << over3 << test1[i] << endl;
        cout << over3 << test2[i] << endl;
        cout << over3 << test3[i] << endl;
        cout << over3 << test4[i] << endl;
        
    }
    return 0;
}

Answer 1

让我们看看您要读取的文件的结构：

Steve 78 65 82 73
Shawn 87 90 79 82
Annie 92 90 89 96
Carol 72 65 65 60
Kathy 34 50 45 20

数据的格式可以描述如下：

每行代表一个 "record"。
每个 "record" 包含多列。
列由空格分隔。

您当前正在为每个 列使用 getline():

for(int i = 0; i < SIZE; i++)
{  
  getline(inputFile, line);
  names[i] = line;
  getline(inputFile, line);
  test1[i] = line;
  getline(inputFile, line);
  test2[i] = line;
  getline(inputFile, line);
  test3[i] = line;
  getline(inputFile, line);
  test4[i] = line;
}

...而您实际上想在一行中读取每个记录并将其拆分：

for (int i = 0; i < SIZE; i++)
{
  string line;
  size_t start = 0;
  // For each line, attempt to read 5 columns:
  getline(inputFile, line);
  names[i] = get_column(line, start);
  test1[i] = get_column(line, start);
  test2[i] = get_column(line, start);
  test3[i] = get_column(line, start);
  test4[i] = get_column(line, start);
}

这是原始代码的修改版本，它按上述方式拆分了每一行：

#include <cctype>
#include <fstream>
#include <iostream>
#include <string>

using namespace std;

static string get_column(string line, size_t &pos)
{
  size_t len = 0;
  // Skip any leading whitespace characters.
  while (isspace(line.c_str()[pos])) { ++pos; }
  // Count the number of non-whitespace characters that follow.
  while (!isspace(line.c_str()[pos+len]) && line.c_str()[pos+len]) { ++len; }
  // Extract those characters as a new string.
  string result = line.substr(pos, len);
  // Update the "start" position (for the next time this function is called).
  pos += len;
  // Return the string.
  return result;
}

int main()
{

  const int SIZE = 5;
  string names[SIZE], test1[SIZE], test2[SIZE], test3[SIZE], test4[SIZE];

  // Ask the user to enter a file name.
  cout << "Please enter your file name: ";
  string fileName;
  cin >> fileName;

  // Open the file and read the data.
  ifstream inputFile(fileName.c_str());
  if (!inputFile.is_open()) { return 0; }

  for (int i = 0; i < SIZE; i++)
  {
    string line;
    size_t start = 0;
    // For each line, attempt to read 5 columns:
    getline(inputFile, line);
    names[i] = get_column(line, start);
    test1[i] = get_column(line, start);
    test2[i] = get_column(line, start);
    test3[i] = get_column(line, start);
    test4[i] = get_column(line, start);
  }

  inputFile.close();

  // Display the data.
  cout << "Student\tTest1\tTest2\tTest3\tTest4" << endl;
  cout << "-------\t-----\t-----\t-----\t-----" << endl;

  for(int i = 0; i < SIZE; i++)
  {
    cout << names[i] << "\t";
    cout << test1[i] << "\t";
    cout << test2[i] << "\t";
    cout << test3[i] << "\t";
    cout << test4[i] << endl;
  }

}

运行程序产生以下输出：

Please enter your file name: textfile.txt
Student Test1 Test2 Test3 Test4
------- ----- ----- ----- -----
Steve   78    65    82    73
Shawn   87    90    79    82
Annie   92    90    89    96
Carol   72    65    65    60
Kathy   34    50    45    20

请注意，get_column() 函数处理多个空格或太短的行，因此此文件：

Steve 78     65 82 73
Shawn   87 90 
Annie 92 90 89 96
Carol 72 
Kathy 34 50   45 20

...产生以下输出：

Please enter your file name: textfile.txt
Student Test1 Test2 Test3 Test4
------- ----- ----- ----- -----
Steve   78    65    82    73
Shawn   87    90
Annie   92    90    89    96
Carol   72
Kathy   34    50    45    20

Answer 2

之前的回答想多了

您可以使用您的输入文件流来检索 'formatted input'（即，您知道格式为 'string' 然后是 'int'、'int' 的输入, 'int', 'int') 与 >> 运算符。

string name;

int score[4];

ifstream mf;

mf.open("score.txt");

// Get name string.
mf >> name;

// Get four score values into an array.
mf >> score[0] >> score[1] >> score[2] >> score[3];

然后：

cout << name;

cout << score[0];
cout << score[1];
cout << score[2];
cout << score[3];

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