C++ filling array issue

Question

I have a function that fills an array based on user input

The program works fine in this test case but it asks the user for one more number than needed.

void fill_array(char a[], int size)
{
char next;
const char SENTIEL ='.';
int index=0;
cin >> next;


  while ((next !=SENTIEL) && (index < size))
{
   a[index] = next;
   index++;
   cin >> next;

}

cout << a[0];
cout << a[1];
cout << a[2];
cout << a[3];
cout << a[4];
cout << a[5];
cout << a[6];
cout << a[7];
cout << a[8];
cout << a[9];   
}




int main()
{
int const MAX=10;
char b[MAX];
fill_array(b,MAX);
}

this returns the correct numbers but it has one more to ask.

you should increment the index at the end of the loop iteration. — Najzero
– Najzero, Commented Mar 26, 2013 at 7:18
What should happen if the user enters less than 10 numbers? Your array will contain garbage after the last entered element. — Michael Wild
– Michael Wild, Commented Mar 26, 2013 at 7:22
Here's the original. Please do not delete questions and re-ask them. It may lead you to a question-ban. — Mysticial
– Mysticial, Commented Mar 26, 2013 at 7:26

sh03 · Accepted Answer · 2013-03-26 07:20:28Z

2

You are asking for cin >> next outside the loop (1 time) then you are asking for cin >> next size time which leads to: size + 1 times.

You should use a for loop (and of course remove the outsider cin >> next):

for (int index = 0; (next !=SENTIEL) && (index < size); index++)
{
   a[index] = next;
   cin >> next;
}

answered Mar 26, 2013 at 7:20

sh03

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Comments

4pie0 · Accepted Answer · 2014-04-08 09:31:16Z

0

please change:

  while ((next !=SENTIEL) && (index < size))
{
   a[index] = next;
   index++;
   cin >> next;

}

to

while ( ( cin >> next) && ( next !=SENTIEL) && ( index < size))
    {
       a[index] = next;
       index++;

    }

also delete frist cin >> next; outside the loop, and obviously initialize next, and it's OK

edited Apr 8, 2014 at 9:31

answered Mar 26, 2013 at 7:24

4pie0

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2 Comments

999k Over a year ago

value of next is garbbage. There is a chance it can be equal to SENTIEL

M.M Over a year ago

This change stores SENTIEL in the array and the original didn't

999k · Accepted Answer · 2013-03-26 07:23:28Z

0

Intialise character next with some other character than SENTIEL and then read next before index is incremented.

char next = ' ';
const char SENTIEL ='.';
int index=0;
while ((next !=SENTIEL) && (index < size))
{
  cin >> next;
  a[index] = next;
  index++;
}

answered Mar 26, 2013 at 7:23

999k

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Comments

Suvarna Pattayil · Accepted Answer · 2013-03-26 07:28:21Z

0

Alternatively you can do something like this,

while ((index < size) && ((cin>>next) && next!=SENTIEL) )
{
   a[index] = next;
   index++;
}

With this, If the 1st input is SENTIEL you won't enter the loop.

answered Mar 26, 2013 at 7:28

Suvarna Pattayil

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