Linked list from file

Below is the method implemented to read from the input file and make it a linked list, I can see that there are two entries inserted from end of the linked list when I diplay the linked list, kindly solve it

I have called it from main() as :

Code:

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parseFile(start, in); // start is the start pointer to the linked list

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Code:

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void parseFile(rectNode *record, ifstream &inFile){
        float coOrdinate;
        char comma;
        if(!inFile.eof())      {
                inFile >> coOrdinate >> comma;
                record->point1.x = coOrdinate;

                inFile >> coOrdinate >> comma;
                record->point1.y = coOrdinate;

                inFile >> coOrdinate >> comma;
                record->point2.x = coOrdinate;

                inFile >> coOrdinate;
                record->point2.y = coOrdinate;

                record->next = (rectNode *) malloc(sizeof(rectNode));

                cout << record->point1.x <<"yes ";
                parseFile(record->next, inFile);
        }
        else    {
                record = NULL;
        }
        return;
}

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The input file is as:

Code:

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0, 0, 10, 10
2, 2, 8, 12
339, 88, 444, 654

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You are leaking memory I believe. When the you reach EOF, record will be NULL, but the previous call of parseFile will have already allocated memory for it.

This makes more sense:

Code:

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void parseFile(rectNode *record, ifstream &inFile){
        float coOrdinate;
        char comma;
        if(!inFile.eof())      {
                record = (rectNode *) malloc(sizeof(rectNode));
                inFile >> coOrdinate >> comma;
                record->point1.x = coOrdinate;

                inFile >> coOrdinate >> comma;
                record->point1.y = coOrdinate;

                inFile >> coOrdinate >> comma;
                record->point2.x = coOrdinate;

                inFile >> coOrdinate;
                record->point2.y = coOrdinate;               

                cout << record->point1.x <<"yes ";
                parseFile(record->next, inFile);
        }
        else    {
                record = NULL;
        }
        return;
}

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So, you allocate memory and initialize the node. If you reach EOF, you simply put NULL to the node, w/o having allocated memory for it.

Also, why use malloc() in C++? Shouldn't you use new? Not that it really matters I guess

Quote:

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Originally Posted by kapil1089thekin

Below is the method implemented to read from the input file and make it a linked list, I can see that there are two entries inserted from end of the linked list when I diplay the linked list, kindly solve it

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The problem may well be the incorrect use of eof() to control the recursion (similiar to the danger of using it to control a loop). I suggest changing the recursion to iteration and more properly testing as you read in, e.g.,

Code:

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void parseFile(rectNode* record, ifstream& inFile) {
    char comma;
    record->next = NULL;
    while (inFile >> record->point1.x >> comma
                  >> record->point1.y >> comma
                  >> record->point2.x >> comma
                  >> record->point2.y) {
        record->next = static_cast<rectNode*>(malloc(sizeof(rectNode)));
        record = record->next;
        record->next = NULL;
    }
}

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Of course, you need to test whether this properly handles invalid input :)

Note that it is actually pointless to assign NULL to record in your original snippet since record is just a parameter that goes out of scope shortly thereafter. You might also want to consider creating an appropriate class type, and then using a std::list of that class type.