Replace all null's in matrix with the phrase Apples

Question

My question is that I would like to get rid of null's by replacing them with the phrase "Apples". If someone can please take a look at my code and tell me where I went wrong and what fix I can apply to do that task that would be great.

Input(Text file):

A B C

E F G

I J K L

char *map[10][10];
int loadMap(char * filename){
    FILE *fp;
    int row = 0;
    int col= 0;

    char buffer[1000];
    char phrase[100] = "pass";

    fp = fopen(filename,"r");
    if(fp == NULL){
      perror(filename);
      return(1);
 }

 char ch;
while (1) {
    fscanf(fp, "%s", buffer);

    map[row][col] = (char *)malloc(sizeof(char) * (strlen(buffer) + 1));

    strcpy(map[row][col], buffer);

    ch = fgetc(fp);

    if (ch == ' ') {
        col += 1;
    }
    else if (ch == '\n') {
        row += 1;
        col = 0;
    }
    else if (ch == EOF) {
        break;
    }
}

 return(0);
}
void DisplayMap(int size){

  int row, columns;

  for (row=0; row<DUNGEONSIZE; row++)
  {
      for(columns=0; columns<DUNGEONSIZE; columns++)
           printf("%s  ", map[row][columns]);
      printf("\n");
   }
  }

Output:

A  B  C  (null)  (null)  (null)  (null)  (null)  (null)  (null)
E  F  G  (null)  (null)  (null)  (null)  (null)  (null)  (null)
I  J  K  L  (null)  (null)  (null)  (null)  (null)  (null)
L  (null)  (null)  (null)  (null)  (null)  (null)  (null)  (null)  (null)
(null)  (null)  (null)  (null)  (null)  (null)  (null)  (null)  (null)  (null)
(null)  (null)  (null)  (null)  (null)  (null)  (null)  (null)  (null)  (null)
(null)  (null)  (null)  (null)  (null)  (null)  (null)  (null)  (null)  (null)
(null)  (null)  (null)  (null)  (null)  (null)  (null)  (null)  (null)  (null)
(null)  (null)  (null)  (null)  (null)  (null)  (null)  (null)  (null)  (null)
(null)  (null)  (null)  (null)  (null)  (null)  (null)  (null)  (null)  (null)

Please provide a [mcve]. Also, what's the input and where's that output coming from (your code as shown has no output)? And finally, take the time to fix up the indentation of your code to make it more readable. — kaylum, Jun 28 '16 at 04:19
And the rest of the [mcve]? You haven't even shown the code that produces that output. — kaylum, Jun 28 '16 at 04:26
`printf("%s ", map[row][columns]);` --> `printf("%s ", map[row][columns] ? map[row][columns] : "Apples");`. This assumes `map` is a global variable (uatomatically initialised to all 0) or has been explicitly initialised to all 0 (again, code you have not shown). — kaylum, Jun 28 '16 at 04:33
Is there a way to put Apples into the array, instead of converting null to Apples in display function. — Arjun Dhiman, Jun 28 '16 at 04:36
`map[row][col] = "Apples";`. Do that for all `map` entries that are not set from the file (or init all the entries to "Apples" and overwrite the relevant entries with the file contents). — kaylum, Jun 28 '16 at 04:39
What's wrong with the obvious: `if(map[row][columns] == NULL) printf("Apples"); else printf("%s ", map[row][columns]);`? — user253751, Jun 28 '16 at 05:13
@Zero -- break bad habits early. Do *NOT* cast the return of `malloc`. It is totally unnecessary. See: [**Do I cast the result of malloc?**](http://stackoverflow.com/q/605845/995714) for thorough explanation. — David C. Rankin, Jun 28 '16 at 06:27
Please edit your post and fix the indention. It's a complete mess - I won't read this question. — Lundin, Jun 28 '16 at 06:46

engineer14 · Accepted Answer · 2016-06-28T05:17:46.817

1

It looks like your problem resides in your display size function. It is going up to the size of the array (map). All the elements you did not get to (due to switching lines/rows) are left uninitialized, in this case, which is NULL.

When displaying, you want to check and make sure it is not NULL. If map was declared as a global variable, you should be okay by checking it is null before displaying (ie if(map[x][y] == NULL...). If it wasn't, you will have to populate the array as shown below.

BTW: as @kaylum said, using printf("%s ", map[row][columns] ? map[row][columns] : "Apples"); in your display function is the must efficient method if map is a global.

Now, if you want to use apples instead. In your populate function, when you see a new line, run from that index until the end and populate with apple. And then after you find your end of file, populate EVERYTHING LEFT with apple:

while{...
 else if (ch == '\n') {
    while (col < 10){ //or col < sizeof(map[0])/sizeof(map[0][0])
       col++
       //malloc map here
       strcpy(map[row][col], "Apple"); }
    row += 1;
    col = 0;
 }...}
 for (; row < 10; row++){ 
  for(; col < 10; col++){ 
    //malloc map[row][col] here
    strcpy(map[row][col],"APPLE");} 
    col = 0;}

edited Jun 28 '16 at 05:17

answered Jun 28 '16 at 04:38

engineer14

607
4
13

Yes, i see that but is there are way to make the null spots in the array hold the pass phrase? Instead of manually displaying it and masking the null. – Arjun Dhiman Jun 28 '16 at 04:40
If you dont mind can you show me "Now, if you want to use apples instead. In your populate function, when you see a new line, run from that index until the end and populate with apple" I am new to c so all this stuff is really confusing at the moment. – Arjun Dhiman Jun 28 '16 at 04:41
there you go @zero – engineer14 Jun 28 '16 at 04:43
@enginer14 look above I posted the output. – Arjun Dhiman Jun 28 '16 at 04:47
whoops, mixed up languages for a sec there. Use strcpy instead of direct assignment btw – engineer14 Jun 28 '16 at 04:49
Yeah, that is what i thought too. – Arjun Dhiman Jun 28 '16 at 04:49
now, what do you want to do for the last line? Basically, a conditional checking for the first element of the array being NULL means you are done. Edit posted – engineer14 Jun 28 '16 at 04:51
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/115782/discussion-between-engineer14-and-zero). – engineer14 Jun 28 '16 at 04:56

Ishan · Answer 2 · 2016-06-28T06:00:26.957

fscanf reads till Either space or '\n'.

First of all, how is NULL represented in the file.

When it reaches NULL, it will stop reading. Now if you have represented NULL as space. You can do fgetc, because it reads till '\n' and continue with your logic. You can declare

char *s = malloc(..) snprintf(s,"%s","Apple")

and assign the char* [][] entries to s.

Do let me know, if I understood wrongly.

while(1)
{
  int num = fscanf(fp, "%s", buffer);
  int ch;
  if(!feof(fp) && num==0)
  // meaning either end of file or not read (space/'\n')
  {
     while(!feof(fp) )
       {
        ch = fgetc(fp);
        if(ch == '\n')
         {
            row += 1;
            col = 0;
            break;
         }
        else if(ch == ' ')
        {

           map[row][col] = strdup("Apple");
           col += 1;
        }
       }
      if(ch == '\n')
        continue;
  }
  if(feof(fp))
     break;

  map[row][col] = (char *)malloc(sizeof(char) * (strlen(buffer) + 1));
  strcpy(map[row][col], buffer); 
}

In your example, once the NULLs start no non null value comes. If it does you can use rewind(fp) to move the pointer 1 step back and continue using fscanf.

can edit my code and show me what you mean I quite understand what you are trying to say? — Arjun Dhiman, Jun 28 '16 at 04:34

Replace all null's in matrix with the phrase Apples

2 Answers2