Reading from input file and storing in array c++ - c++

Question

I want to read from a file.txt that looks like this:
process_id run_time
T1 23
T2 75
Read each line and store integers of run time (tab separation)in an array
My problem now is to read the content of the file .. and how to get the integer after the tab separation?
thanks
#include <iostream>
#include <fstream>
#include <cstdlib>
using namespace std;
int main ()
{
int process_id[100];
int run_time[100];
int arrival_time[100];
char quantum[50];
int switching;
char filename[50];
ifstream ManageFile; //object to open,read,write files
cout<< "Please enter your input file";
cin.getline(filename, 50);
ManageFile.open(filename); //open file using our file object
if(! ManageFile.is_open())
{
cout<< "File does not exist! Please enter a valid path";
cin.getline(filename, 50);
ManageFile.open(filename);
}
while (!ManageFile.eof())
{
ManageFile>>quantum;
cout << quantum;
}
//ManageFile.close();
return 0;
}

Answer 1

use C++, not C
don't use std::cin.getline, use std::getline (it works with std::string and is safer)
use a vector instead of hard-dimensioned arrays
use a vector of struct instead of "corresponding arrays"
don't use while (!stream.eof())
Here's a sample that might be helpful:
#include <iostream>
#include <fstream>
#include <sstream>
#include <vector>
#include <string>
using namespace std;
struct Record {
int process_id;
int run_time;
int arrival_time;
};
int main() {
std::vector<Record> records;
int switching;
std::string filename;
ifstream infile;
while (!infile.is_open()) {
cout << "Please enter your input file: ";
std::getline(std::cin, filename);
infile.open(filename); // open file using our file object
cout << "File cannot be opened.\n";
}
std::string quantum;
std::getline (infile, quantum); // skip header row
while (std::getline(infile, quantum)) {
// e.g.
Record current;
std::istringstream iss(quantum);
if (iss >> current.process_id >> current.run_time >> current.arrival_time)
records.push_back(current);
else
std::cout << "Invalid line ignored: '" << quantum << "'\n";
}
}

Answer 2

You can try something like this:
while (!ManageFile.eof())
{
quantum[0] = 0;
ManageFile>>quantum;
if (strcmp(quantum, "0") == 0 || atoi(quantum) != 0)
cout << quantum << endl;
}
Of course, you need to include in the head

Answer 3

Use function ignore from istream [http://www.cplusplus.com/reference/istream/istream/ignore/]
while (!ManageFile.eof())
{
std::string process_id;
int run_time;
ManageFile >> process_id;
ManageFile.ignore (256, '\t');
ManageFile >> run_time;
}

Answer 4

Using fscanf instead of ifstream can make the job a lot easier.
char str[100];
int n;
....
fscanf(FILE * stream,"%s %d", str, &n);
You will get the string in str and integer in n.