C++ - inputting and outputting multiple integers with io redirection

Question

I'm new to C++ and writing a simple program that should take integers from a file as ints and output them formatted appropriately. The issue is that the program skips one of the values when outputting. eg (\n representing a new line) "51 123\n -10\n 153 111" would come out as "123\n -10\n 153\n 111\n 0". Also any tips or pointers for bettering my code would be great. Here is my code:

using namespace std;

int main(int argc, char *argv[]) {
    size_t i;
    int n;
    int a, b, c, d, e;
    if (argc == 1) {
        while (cin >> n) {
            cin >> a;
            cin >> b;
            cin >> c;
            cin >> d; 
            cin >> e;
            cout << setw(10);
            cout << a << "\r\n";
            cout << setw(10);
            cout << b << "\r\n";
            cout << setw(10);
            cout << c << "\r\n";
            cout << setw(10);
            cout << d << "\r\n";
            cout << setw(10);
            cout << e;
        }
    } else if (strcmp(argv[1],"-x")==0) {
        /* not used yet */
    } else if (strcmp(argv[1],"-o")==0) {
        /* not used yet */
    }
}

You are reading a number into n using while ( cin >> n ). That number is not being written out to cout. — R Sahu
– R Sahu, Commented Jun 2, 2016 at 4:58

R Sahu · Accepted Answer · 2016-06-02 05:01:52Z

1

Problem 1:

You are reading a number into n using while ( cin >> n ). That number is not being written out to cout. That means, the first number is being read and discarded.

Problem 2:

The line cin >> e; does not really read anything into e. That's why you have 0 in the output.

Suggested Fix:

Read all the numbers in the conditional of the while.

while (cin >> a >> b >> c >> d >> e)
{
   cout << setw(10);
   cout << a << "\r\n";
   cout << setw(10);
   cout << b << "\r\n";
   cout << setw(10);
   cout << c << "\r\n";
   cout << setw(10);
   cout << d << "\r\n";
   cout << setw(10);
   cout << e;
}

answered Jun 2, 2016 at 5:01

R Sahu

207k15 gold badges168 silver badges291 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Bobbis Over a year ago

Thanks a bunch, works and your answer led me to this:

while (cin >> n ) { 			 			if (n < 0) {cout << "-";} else {cout << "+";} 			cout << setw(10);		 			cout << abs(n) << "\r\n"; 		}

R Sahu Over a year ago

@Bobbis, glad I was able to help.

Falla Coulibaly · Accepted Answer · 2016-06-02 05:06:58Z

0

You while loop condition : while(cin >> n) will try to store an integer in your variable n and return true if the cin >> n succeeded thus allowing you to go inside the loop. I don' really see the point of using a loop if all your data is in a file and your are not using an array/vector to iterate through the file to get the file. Using an array will be way effective e.g:

int values[NUMBER_OF_ELEMENTS]; // if number of elements is known
std::vector<int> values;// Use vector otherwise

In any case remove your while loop condition as a well as the braces associated to it and your code should run as expected.

answered Jun 2, 2016 at 5:06

Falla Coulibaly

7692 gold badges11 silver badges23 bronze badges

Collectives™ on Stack Overflow

C++ - inputting and outputting multiple integers with io redirection

2 Answers 2

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related