reading array format input

Question

Can you, please, help to get input of this format:

{1,2,3,4}

and convert it to array with integers?

    int * ns = new int [n];
    cin >> ns;

This does not work. How should I change it?

As it's c++, first part of the answer will be "use `std::vector` instead of `new int[n]`". — Anton Kovalenko, Feb 13 '13 at 12:49

score 0 · Answer 1 · answered Feb 13 '13 at 12:50

0

using namespace std;
typedef istream_iterator<int> It;
vector<int> v;
copy(It(cin), It(), back_inserter(v));

answered Feb 13 '13 at 12:50

John Zwinck

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You can read the documentation of the functions I used. It just copies all the s that it can from std::cin to the vector. – John Zwinck Feb 13 '13 at 12:56
Sure, the OP wasn't very clear about the input requirements...he/she should look at http://stackoverflow.com/a/1895584/4323 for a more elaborate explanation of how to make it support commas. Or write it a different way completely! – John Zwinck Feb 13 '13 at 12:59
I have tried the code. It read elements until a non-digit, non-\n character is entered from stdin. For example, if I type `12\n34\n56\n,` , v would contains {12, 34, 56} EDIT: `CTRL+D` can also be used to terminate the input. – Konfle Dolex Feb 13 '13 at 12:59

score 0 · Answer 2 · answered Feb 13 '13 at 13:02

You need to read the elements one by one and store them into the array.

int aNoOfElements = 0;
cin >> aNoOfElements;
int *anArray = new int[ aNoOfElements];     //allocate memory to hold aNoOfElements

for( int i = 0; i < aNoOfElements; i++ )
{
     cin >> anArray[ i ];                   // Read each input
}

score 0 · Answer 3 · answered Feb 13 '13 at 13:07

You need to parse the input. Take the input as string, then check for the format conforming to what you want. An algorithm that you can use:

Check whether the first character is '{'
If yes, then initialize a variable (say temp) to hold the number that you're about to get (as a string) with empty string, else error
read next character
if it's between '0' and '9' then append it to temp and go back to step 3, else go to step 5
if it's a comma or '}', then convert temp to integer and put it into the array, re-initializing temp with empty string, else error
still on the same character, if it's a comma then go back to step 3, otherwise done

I hope you can turn above algorithm into working code, good luck :)

P.S.: Feel free to tell me if you spot a bug

reading array format input

3 Answers3