Trouble with pointers and reading information into an array - c++

Question

I'm having some issues when trying to read in some values to a dynamically allocated array. Everything looks okay to me, but when the code is run, only the last entry into the array is shown. The code is below. If you could give me some recommendations I would appreciate it.
ifstream infile;
infile.open("MovieStatistics.txt");
int numOfStudents = 0;
string first, last, line;
int movies;
int *numMovies = nullptr;
string *names = nullptr;
if (!infile) {
cout << "Error opening file";
} else {
while (getline(infile, line)) {
numOfStudents++;
stringstream ss(line);
ss >> first >> last >> movies;
}
numMovies = new int[numOfStudents];
names = new string[numOfStudents];
}
for (int i = 0; i < numOfStudents; i++) {
names[i] = first + " " + last;
numMovies[i] = movies;
}

Answer 1

Your problem is you assign first and last inside the read loop but you don't store the values in an array or vector so they contain the last values.
To get it to work you could edit the code to:
ifstream infile;
infile.open("data.txt");
int numOfStudents = 0;
string first, last, line;
int movies;
int *numMovies = nullptr;
string *names = nullptr;
// get the number of students
while (getline(infile, line))
numOfStudents++;
numMovies = new int[numOfStudents];
names = new string[numOfStudents];
// clear the buffer
infile.clear();
infile.seekg(0, ios::beg);
int i = 0;
while(getline(infile, line)){
stringstream ss(line);
ss >> first >> last >> movies;
names[i] = first + " " + last;
numMovies[i] = movies;
++i;
}
for(int i = 0; i < numOfStudents; i++)
cout << names[i] << endl;
// don't forget to free memory:
delete[] movies;
delete[] names;
infile.close();
What I recommend is to use class vector:
std::ifstream infile("data.txt");
std::string sLine;
std::vector<std::string> vecNames;
while(getline(infile, sLine))
vecNames.push_back(sLine);
auto size = vecNames.size();
//for(auto x : vecNames)
// std::cout << x << std::endl;
for(int i(0); i != size; ++i)
std::cout << vecNames[i] << std::endl;
infile.close();

Answer 2

So you loop over the file, repeatedly reading data into first, last and movies — overwriting the previous values each time.
Much later, you take the current value of those variables, and write it to your dynamic arrays numOfStudents times.
You probably want to rewind the stream and loop over the file again so that you can pull out all the data; you never actually stored each sample the first time around.