template<class vType, int size>
void graphType<vType, size>::createGraph()
{
     ifstream infile;
     char fileName[50];
 
     vType vertex;
     vType adjacentVertex;
 
     if(gSize != 0)  //if the graph is not empty, make it empty
        clearGraph();
 
     cout<<"Enter the input file name: ";
     cin>>fileName;
     cout<<endl;
 
     infile.open(fileName);
 
     if(!infile)
     {
        cerr<<"Cannot open the input file."<<endl;
        return;
     }
 
     infile>>gSize;  //get the number of vertices
 
     for(int index = 0; index < gSize; index++)
     {
         infile>>vertex;
         infile>>adjacentVertex;
 
         while(adjacentVertex != -999)
         {
             graph[vertex].insertLast(adjacentVertex);
             infile>>adjacentVertex;
         }//end while
     }//end for
 
     infile.close();
}//end createGraph

5
0 1 4 3 -99
1 2 -99
2 -99
3 4 1 -99
4 2 1 -99

#include <iostream>
#include <sstream>
#include <string>
 
std::string line;
for(int row = 0; std::getline(infile, line); row ++) {
    std::istringstream stream(line);  // create a stringstream with the line from the file
    int number;
    while(stream >> number) {
        graph[row].insertLast(number);
    }
}