How to read from a specific line in a file (C++) - c++

Question

I need to find enter a number and find the specific line in my text file to correspond with the number, and I am having a little trouble, heres what I have so far:
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

Yes, you use a for loop to loop until you reach the line number, while incrementing.
#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;
}

Answer 2

This will helps : )
#include<iostream>
#include<vector>
#include<fstream>
#include<string.h>
#include<iomanip>
using namespace std;
int main()
{
int number;
cout << "Please enter the ID number of the student, to view their grades: ";
cin >> number;
ifstream myfile;
myfile.open("grades.txt");
if (myfile)
{
string string_obj;
string delimiter = " ";
int id,exam1,exam2,exam3;
size_t pos = 0;
cout << " ID exam1 exam2 exam3" << endl;
cout << "---------------------------------" << endl;
getline(myfile, string_obj);
//Split string into tokens
string token[4];
int i=0;
while ((pos = string_obj.find(delimiter)) != string::npos)
{
token[i++] = string_obj.substr(0, string_obj.find(delimiter));
string_obj.erase(0, pos + delimiter.length()); // move string for next iteration
}
token[i] = string_obj.substr(0, string_obj.find(delimiter));
id = stoi(token[0]);
if (id == number)
{
exam1 = stoi(token[1]); // convert string into int
exam2 = stoi(token[2]);
exam3 = stoi(token[3]);
}
cout << setw(5) << number << setw(9) << exam1
<< setw(9) << exam2 << setw(9) << exam3 << endl;
cout << "---------------------------------" << endl;
int total = exam1 + exam2 + exam3;
cout << "TOTAL: " << setw(25) << total << endl << endl;
}
myfile.close();
return 0;
}