How can I get limitless inputs in a line seperated with spaces?

Question

What I am trying to do is overloading the >> operator of my Book class to take an unknown number of integers from the user in one line. After that, I need to create an array of them.

I tried this:

istream& operator>>( istream& in, Book& b )
{
    int x;

    delete[] b.editionYears;
    b.editionNo = 0;
    b.editionYears = new int[0];

    cin>>x;

    b.addEdition(x);

    return in;
}

And I call this with

cout << A << endl;

in the test class where A is a Book object.

I tried this but in here, when the user enters something like "1 2 3 4", it only deletes the array and adds 1 to it, in the second call it deletes 1 again and adds 2.

What I expect is, if the user enters "1 2 3 4", it should delete editionYears array, create again and add 1,2,3,4 to it.

So how can I do this? Thanks for any help.

I thought using a loop but how can I get the number of elements to use in the loop? If the user enters 3 inputs, the loop should be executed 3 times but how can I get 3? — Berdan Akyürek, Mar 31 '19 at 11:34
There are two ways to tell the end of some input: Provide the length of the input, or use some kind of sentinel. If you can't have either, then there's really no way of solving your problem. — Some programmer dude, Mar 31 '19 at 11:38

Aykhan Hagverdili · Answer 1 · 2019-03-31T11:54:47.070

Consider using std::vector instead of dynamically allocated arrays. There are multiple ways to do this. You may ask users to enter the number of integers they are going to enter, you may ask them to enter something like -1 when they are done, or you may ask them to enter all the integers in a single line, then read it into stringstream then convert to ints and push_back to a vector. The first two approaches are trivial to implement, so here's an example implementation for the third way:

#include <iostream>
#include <vector>
#include <sstream>

int main()
{
  std::vector<int> vec;
  std::cout << "please enter numbers in a line" << std::endl;
  std::string line;
  std::getline(std::cin, line);
  std::istringstream ss(line);
  int i;
  while (ss >> i)
  {
    vec.push_back(i);
  }

  return 0;
}

score 1 · Accepted Answer · answered Mar 31 '19 at 11:56

1

Your problem is in the use of cin. Try using std::getline.

This other answer may help https://stackoverflow.com/a/5838803/5355195

answered Mar 31 '19 at 11:56

CarlosAlbaladejo

90
2
8

How can I get limitless inputs in a line seperated with spaces?

2 Answers2