c++ - 如何从文件中的特定行读取 (C++)

Question

我需要找到输入一个数字并在我的文本文件中找到与该数字相对应的特定行，我遇到了一点麻烦，这是我目前所拥有的:

cout << "Please enter the ID number of the student, to view their grades: ";
cin >> number;

ifstream myfile;
myfile.open("grades.txt");
if (myfile)
{
    cout << "  ID      exam1    exam2    exam3" << endl;
    cout << "---------------------------------" << endl;

    getline(myfile, number);
    myfile >> number >> exam1 >> exam2 >> exam3;


    cout << setw(5) << number << setw(9) << exam1
        << setw(9) << exam2 << setw(9) << exam3 << endl;
    cout << "---------------------------------" << endl;

    total = exam1 + exam2 + exam3;
    cout << "TOTAL: " << setw(25) << total << endl << endl;
}
myfile.close();
return 0;

Answer 1

是的，您使用 for 循环循环直到到达行号，同时递增。

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

int main()
{
  // Line #
  int line;
  // File
  std::ifstream f("_"); 
  // Text
  std::string s; 

  // Prompt
  std::cout << "Line #: " << std::endl; 
  // Store line #
  std::cin >> line; 

  // Loop, while less than line
  for (int i = 1; i <= line; i++)
    std::getline(f, s);

  // Output text at line
  std::cout << s;
  return 0;
}