Determining the size of an array needed to store unknown amount of integers

[sesch]

Let's say you have a text file with x amount of numbers stored one by one in seperated text lines, you load them all word by word into a string and then convert them to integers and store in array of integers like this :

ifstream file("blablabla.txt");
string s;
int i = 0;
int array[ ??? ];
while(file>>s){
  istringstream ss(s);
  ss = array[i];
  i++;
}

So the question is - how do you know how wide your array must be ? Until now I just made an array of 10k elements to make sure all the loaded files will not cause any errors(unless there are more than 10000 of numbers in them), but I know it is not the right thing to do, how to determine size of my array ?

[Moschops]

This being C++, you can avoid having to deal with it yourself by using a proper C++ container. For example, a vector of int types:

vector<int> array;

and then simply add each int as you read them in using the push_back class function.

http://www.cplusplus.com/reference/stl/vector/

[IceThatJaw]

if all the numbers are separated by spaces you can simply read through the file counting how many their are and then allocate it dynamically.

But I would use the STL list to be honest. Vectors are easier but are not as efficient when you are constantly adding to them dynamically.

[sesch]

Thanks guys, I thought about the first option IceThatJaw, to be honest that is how I'm planning to do this for now, but vectors sound more logic though, anyway cheers for the help.

[andywestken]

You can make a vector's push_back more efficient be reserving space, if you have a rough idea about how many elements you're expecting.

Another possibility is to use a deque, unless you need the storage to be contiguous. The memory for a deque is allocated in chunks, so the resizing of the array is more efficient.