Issues with while loop and reading from files - c++

Question

I'm working on this project and I'm fairly new to C++. Its kind of hard to explain what I'm trying to do but I shall try. So I'm working with a file called flix.txt and in it looks like the following:
1 A 5
1 B 4
1 D 3
1 F 5
2 A 1
3 E 3
3 F 1
4 A 2
The first column are people(my objects), second columns are movies, and the third are the ratings given by the objects.
I'm trying to first extract the first int from every line and create an object using an 'operator new'. Then I'm taking a movie and turning it into an int so I can plug the rating into an array. Sorry if it sounds confusing. Heres the code I have now:
//flix program
#include <iostream>
#include <string>
#include <fstream>
#include <sstream>
#define NUMBER_OF_MOVIES 6
using namespace std;
int tokenize(string line);
int getMovieNum(char movie);
void resetPos(istream& flix);
class Matrix{
public:
int movieRate[NUMBER_OF_MOVIES];
};
int main(){
int distinctCount = 0;
int checker = -1;
int check = 0;
string line;
int personNum;
char movie;
int rating;
int movieNum;
ifstream flix("flix.txt");
ofstream flick("flix1.txt");
//identify distinct account numbers in file
while(getline(flix, line)){
check = tokenize(line);
if(check != checker)
distinctCount++;
checker = check;
check = 0;
}
//reset position in file
resetPos(flix);
//create objects in accordance with distinct numbers
Matrix* person = new Matrix[distinctCount];
for(int i = 0; i < distinctCount; i++){
for(int j = 0; j < NUMBER_OF_MOVIES; j++){
person[i].movieRate[j] = 0;
cout << i + 1 << ' ' << person[i].movieRate[j] << endl;
}
cout << "\n";
}
//reset position in file
resetPos(flix);
//get data from file and put into respective variables
while(getline(flix, line)){
flix >> personNum >> movie >> rating;
cout << personNum << ' ' << movie << ' ' << rating << endl;
//changes the char into an int
movieNum = getMovieNum(movie);
person[personNum].movieRate[movieNum] = rating;
}
//reset position in file
resetPos(flix);
//input ratings into movie array
for(int i = 0; i < distinctCount; i++){
for(int j = 0; j < NUMBER_OF_MOVIES; j++){
cout << i + 1 << ' ' << person[i].movieRate[j] << endl;
flick << i + 1 << ' ' << person[i].movieRate[j] << endl;
}
}
//write data to text file
//??
flick.close();
//free memory
delete[] person;
system("pause");
return 0;
}
int tokenize(string line){
string myText(line);
istringstream iss(myText);
string token;
getline(iss, token, ' ');
int strInt = atoi(token.c_str());
return strInt;
}
int getMovieNum(char movie){
int movieNum = 0;
switch(movie){
case 'A':
movieNum = 1;
break;
case 'B':
movieNum = 2;
break;
case 'C':
movieNum = 3;
break;
case 'D':
movieNum = 4;
break;
case 'E':
movieNum = 5;
break;
case 'F':
movieNum = 6;
break;
default:
movieNum = 0;
break;
}
return movieNum;
}
void resetPos(istream& flix){
flix.clear();
flix.seekg(0);
}
I also apologize in advance if there are noobish mistakes here.
I think the problem is somewhere in the while loop, that's where it keeps locking up. I spent hours on this and I can't figure out why it doesn't work. In the while loop, I'm trying to access every line of the file, snag the data from the line, take the movie char and turn it into an int, and then plug the data into the array within the object. When I did have it working, all the data was wrong too. Any input is highly appreciated. Thanks in advance.

Answer 1

You need to change a little in your program and i'l paste only the changed part.
Somewhere after you reset the person[].movieRate[] to zero,you have written this while loop
resetPos(flix);
int k = NUMBER_OF_MOVIES + 2; //this is the variable that i have declared
//get data from file and put into respective variables
while(k){ //do you see that instead of getline() i have used the variable k. i'l tell you why later
flix >> personNum >> movie >> rating;
//personNum = tokenize(line,1);
cout << personNum << ' ' << movie << ' ' << rating << endl;
//changes the char into an int
movieNum = getMovieNum(movie);
person[personNum - 1].movieRate[movieNum] = rating; //this is personNum-1 and NOT personNum the most common mistake while indexing array.
k--;
}
this code seems to work as your criteria.
the reason that i removed getline() is, if u call getline then the get pointer position will be incremented. so after this you call flix >> something... , this reads the data from the second line. your first line 1 A 5 is lost. this was the cause of the trouble. change it n let me know.

Answer 2

Okay, let me try to give at least some idea of a simple starting point:
#include <iostream>
#include <iterator>
#include <vector>
#include <fstream>
struct rater {
std::vector<int> ratings;
rater() : ratings(6) {}
friend std::istream &operator>>(std::istream &is, rater &r) {
char movie;
is >> movie;
return is >> r.ratings[movie-'A'];
}
friend std::ostream &operator<<(std::ostream &os, rater const &r) {
for (int i=0; i<r.ratings.size(); i++) {
os << char(i + 'A') << ":" << r.ratings[i] << "\t";
}
return os;
}
};
int main() {
std::ifstream in("flix.txt");
std::vector<rater> ratings(5);
int i;
while (in >> i)
in >> ratings[i-1];
i=1;
for (auto r : ratings)
std::cout << i++ << "-> " << r << "\n";
}

Answer 3

Here's a bit of a clean up. It uses std::map to keep track of the Person and Movie keys, which is more flexible as textual strings of any kind (sans whitespace) can be used. You've added a comment saying you specifically want to list movies people didn't rate in their outputs - that can be done by using a std::set and ensuring each movie name encountered is inserted, then using an iteration over the set to guide lookups in each person's ratings: left as an exercise.
#include <iostream>
#include <string>
#include <fstream>
#include <sstream>
#include <map>
using namespace std;
typedef std::map<std::string, int> Movie_Ratings;
typedef std::map<std::string, Movie_Ratings> Persons_Movie_ratings;
int main()
{
if (!ifstream flix("flix.txt"))
{
std::cerr << "error opening input\n";
exit(1);
}
if (!ofstream flick("flix1.txt"))
{
std::cerr << "error opening output\n";
exit(1);
}
Persons_Movie_Ratings ratings;
std::string line;
while (getline(flix, line))
{
istringstream iss(line);
string person, movie;
int rating;
if (line >> person >> movie >> rating)
ratings[person][movie] = rating;
}
// input ratings into movie array
for (Persons_Movie_Ratings::const_iterator i = ratings.begin();
i != ratings.end(); ++i)
{
for (Movie_Ratings::const_iterator j = i->second.begin();
j != i->second.end(); ++j)
{
cout << i->first << ' ' << j->second << endl;
flick << i->first << ' ' << j->second << endl;
}
}
system("pause");
}