problems with 2d arrays..

mgdpetter · #1 25-May-2004, 22:01

Hi, im stuck again...

Small problem...
multidimensional arrays.
Can i first create a 2 dimensional array of characters like this:

CPP / C++ / C Code:

char string[7][7];

and then in some other function initialize it?
I tried this, but no luck...

CPP / C++ / C Code:

strcpy(string, {{' ',' ',' ',' ',' ',' ',' '},
                     {' ',' ',' ',' ',' ',' ',' '},
                     {' ',' ',' ',' ',' ',' ',' '},
                     {' ',' ',' ',' ',' ',' ',' '},
                     {' ',' ',' ',' ',' ',' ',' '},
                     {' ',' ',' ',' ',' ',' ',' '},
                     {' ',' ',' ',' ',' ',' ',' '}});

Is there any other way??

aaroncohn · #2 25-May-2004, 22:34

Do you know how to loop yet? A common and effective way of initializing arrays of any dimension is to use a "for loop" to go through the array setting each element to the value of your desire.

CPP / C++ / C Code:

int main()
{
  char string[7][7];

  for (int x = 0; x < 7; x++)
    for (int y = 0; y < 7; y++)
      string[x][y] = '\0'; // NULL character

  return 0;
}

Max Payne · #3 25-May-2004, 22:35

Here is one way, but not the easy way I think:

CPP / C++ / C Code:

char string[7][7];// = {NULL};
for(int i=0;i<7;i++)
for(int j=0;j<7;j++)
	string[i][j]=NULL;

aaroncohn · #4 25-May-2004, 22:36

Beat you

Max Payne · #5 25-May-2004, 22:39

yes u did,I'm one minute late... Damn, my typing is still slow...

mgdpetter · #6 26-May-2004, 02:17

Quote:

Originally Posted by aaroncohn

Do you know how to loop yet? A common and effective way of initializing arrays of any dimension is to use a "for loop" to go through the array setting each element to the value of your desire.

CPP / C++ / C Code:

int main()
{
  char string[7][7];

  for (int x = 0; x < 7; x++)
    for (int y = 0; y < 7; y++)
      string[x][y] = '\0'; // NULL character

  return 0;
}

That works if i want to fill every element with NULL characters, but i want to do something else.. first i want to create an array ,which is [7][7], and then i take a character and use a switch statement to check what character that is and then initialize the array accordingly.
My code looks a bit like this:

CPP / C++ / C Code:


char a[ROWS][COLUMNS]={{' ',' ',' ',' ',' ',' ',' '},
                       {' ','@','@','@',' ',' ',' '},
                       {' ',' ',' ',' ','@',' ',' '}
                       {' ',' ',' ',' ','@',' ',' '},
                       {' ',' ','@','@','@',' ',' '}
                       {' ','@',' ',' ','@',' ',' '},
                       {' ','@','@','@','@',' ',' '}};
      
   
char b[ROWS][COLUMNS]={{' ','@',' ',' ',' ',' ',' '},
                       {' ','@',' ',' ',' ',' ',' '},
                       {' ','@',' ',' ',' ',' ',' '},
                       {' ','@','@','@',' ',' ',' '},
                       {' ','@',' ',' ','@',' ',' '},
                       {' ','@',' ',' ','@',' ',' '},
                       {' ','@','@','@','@',' ',' '}};

in other words, im trying to represent every lower case letter as a 2d array representation of that character built of @.
But i dont want to initialize every 26 letters, but rather declare only one array and then have some kind of switch statement to decide how to initialize it. Can it be done?

Max Payne · #7 26-May-2004, 02:38

If this is what you want, I could give an idea of how to do this.

first, take a piece of paper and draw a 7X7 grid and fill in the '@' so that it makes and 'a'. Now, List down all the position in the array which contains the '@'. In your prev post, the char a contains '@' in the following positions:

(1,1),(1,2),(1,3),(2,4),(3,4),(4,2),(4,3),(4,4),(5 ,1),(5,4),(6,1),(6,2),(6,3),(6,4).

do the same with b,c,d...z

Now, put all the positions for each char in a struct or array or even a file.. chose what suits your need.

CPP / C++ / C Code:

char chr;
cout<<"Enter a char :";
cin>>chr;
switch (chr)
{
  case 'a':
  //here u get the list of position for the the char 'a' and put '@' at the
  //corresponding position in your a[][] array.
  break;
}

// thats just a pseudokod to guide,try to program and if you have a problem with that, post it here!!

mgdpetter · #8 26-May-2004, 21:19

That worked very well. thank you.
Now i only have one small little problem left..
im using

CPP / C++ / C Code:

scanf()

to make the user type in a string and then convert that string to the combinations of @ that you showed me how to do.
Its just that if the user types two strings separated by ' ' (blank space) the scanf function stores the second string as well, (or something like that), and that causes problems for me...
Is it possible to remove any remaining parts of the string, i've read something about

CPP / C++ / C Code:

fflush()

but dont't know if/how it works...
thanx

Max Payne · #9 26-May-2004, 22:54

Well, I use scanf and fflush but there was a thread where another member suggested that I shouldnot be using it cause it may or may not work..

so you can use the fgets ot getline function or even the >> ooperator to get input.

but just how to use scanf and fflush:

CPP / C++ / C Code:

  scanf("%s",array[i]);
  fflush(stdin);

WaltP · #10 26-May-2004, 23:10

Quote:

Originally Posted by mgdpetter

That worked very well. thank you.
Now i only have one small little problem left..
im using

CPP / C++ / C Code:

scanf()

to make the user type in a string and then convert that string to the combinations of @ that you showed me how to do.
Its just that if the user types two strings separated by ' ' (blank space) the scanf function stores the second string as well, (or something like that), and that causes problems for me...
Is it possible to remove any remaining parts of the string, i've read something about

CPP / C++ / C Code:

fflush()

but dont't know if/how it works...
thanx

fflush() is undefined for the input stream, and scanf() has lots of problems.

Since all you want to do is read a string, use fgets(). It's the best you can get for string input.

Are you saying the space is causing problems? Why should it cause trouble?

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problems with 2d arrays..

thanx, but doesnt work..

aha..