CODEWITHSUNDEEP
c++
benpva16
benpva16

Reputation: 454

Loop through a file once, reading lines into objects added to an array

I am reading through a file where each line represents an object I will add to an array. I do not know in advance how many lines are in the file, and I can only loop through it once. In addition, I am restricted to using plain arrays - no other container or collection classes. Here's what I've got:

ifstream f;
f.open("lines.csv");

string line;
string theCode;
string theName;
Manufacturer **manufacturers = new Manufacturer*[752]; // this number can't be here - I have to allocate dynamically
int index = 0;

while(getline(f, line))
{
    theCode = line.substr(0, 6);
    theName = line.substr(7, string::npos);
    Manufacturer* theManufacturer = new Manufacturer(atoi(theCode.c_str()), theName);
    manufacturers[index++] = theManufacturer;
}

Upvotes: 0

Views: 45

Answers (1)

findall
findall

Reputation: 2193

You need to re-allocate a wider array every time when the index reaches the end of a current array. Like this.

int capacity = 752;
while(getline(f, line))
{
    if (capacity <= index) {
        capacity = (capacity+1) * 2;
        Manufacturer **tmp = new Manufacturer*[capacity];
        std::copy(manufacturers, manufacturers+index, tmp);
        delete[] manufacturers;
        manufacturers = tmp;
    }
    /* ... */;
}

Upvotes: 1

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