Extract data from file into vectors but avoid duplicates - c++

Question

I want to read data in files that are formatted like:
Point1, [3, 4]
I'm using delimiters '[' ']' and ',' and replace them with ' ' (empty space). My code now is fine and working. But the problem is, if Point1, [3, 4] appeared once, I want it to be unique and not to appear again if the same data in the text file exist.
Here is what I have:
string line, name;
char filename[50];
int x,y;
cout << "Please enter filename : ";
cin >> filename;
ifstream myfile(filename);
if (myfile.is_open()) {
while ( myfile.good() ) {
getline(myfile, line);
for (unsigned int i = 0; i < line.size(); ++i) {
if (line[i] == '[' || line[i] == ']' || line[i] == ',') {
line[i] = ' ';
}
istringstream in(line);
in >> name >> x >> y;
}
cout <<name <<endl;
if (name=="Point") {
p.push_back(Point(x,y));
}
count++;
}
myfile.close();
cout << count;
}
else cout<< "Unable to open file";
How do i do this? I tried adding this after if(name=="Point")
for (int j=0; j<p.size(); j++) {
if(p.getX != x && p.getY) != y) {
p.push_back(Point(x,y))
}
}
...but this is not working properly as data was not stored into the vector.
Anyone can help?

Answer 1

Instead of storing your data into vectors you can store it into sets. A set contains only unique values, so you don't have to check the uniqueness of your Points, the set will manage that.
Instead of defining vector<Point>, you have to define set<Point>, and instead of using p.push_back to add points into your vector, you have to use p.insert if it is a set.
You can check the set documentation here.

Answer 2

Assuming you want to keep you data store in a std::vector<Point> you could just check that no corresponding point already exists. Assuming there is an equality operator defined, it is as easy as this:
if (p.end() == std::find(p.begin(), p.end(), Point(x, y))) {
p.push_back(Point(x, y));
}
If you Point type doesn't have an equality operator and shouldn't get one, you can use a function object together with find_if() instead, e.g.:
if (p.end() == std::find_if(p.begin(), p.end(),
[=](Point const& v) { return x == v.x && y == v.y; })) {
...
You should separate your loops from other operations: The loop you propose to check if the point already exists is basically what std::find() does except that you insert a new point in each iteration! You first want to go through all existing points and see if it exists anywhere. Only if it does not, you'd insert a new point.
Note, that you did a similar mistake when replacing characters in your string: you try to decode the string after checking each character. This isn't so much a semantic problem but it is a major performance problem. You should replace the characters in a loop and after that loop you should decode the string just once. Of course, when decoding the string you need to check if the format was OK as it is always necessary to determine if an input operation was successful. That is, after your loop replacing the characters you want something like:
std::istringstream in(line);
if (in >> name >> x >> y) {
// now process the data
}
... or, if you are like me and don't like naming things which are only around temporarily:
if (std::istringstream(line) >> std::ws >> name >> x >> y) {
As another note: checking a stream for good() is generally the wrong thing to do because a stream can be in perfectly good conditions except that it had seen EOF at some point and, thus, as set the std::ios_base::eofbit. More importantly, you need to check after the input operation, not before! That is, your first loop should start with something like this:
while (std::getline(myFile, line)) {
...