A function to count the amount of unique chars in a 2D array

I'm attempting to create a function that counts the number of unique characters in a 2D char array (even if 'a' occurs 4 times, it just counts it as one occurence) and the function returns true/false depending on whether the number of unique chars is higher or lower than the width or height of the grid.


I am stuck as my function is not working and I assume it's because i & j both = 0 so it is true on the first iteration. However I cannot figure out how to remedy this and create a working function, so any help would be great.

Code:

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#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <assert.h>


#define MAXGRIDHW 9
#define FRONT -1
#define REAR -1


typedef enum bool{ false = 0, true = 1 } bool;


typedef struct node{
    char grid[MAXGRIDHW][MAXGRIDHW];
    int height;
    int width;
    int parent;
} Node;


bool uniqueChars(Node* b);
void setHeightWidth(Node* b, int h, int w);
void clearNode(Node* b);


int main (void)
{
    Node shelf1[10];


    char testArr2[3][4] = {{"z.."},
                          {"q.."},
                          {"z.."}};


  clearNode(&shelf1[1]);


  memcpy(&shelf1[2].grid, testArr2, 7);


  setHeightWidth(&shelf1[2], 3, 4);


  assert(uniqueChars(&shelf1[2]) == true);


  return 0;
}


void clearNode(Node* b)
{
    int i, j;


    b->height = 0;
    b->width = 0;
    b->parent = FRONT;


    for (i = 0; i < MAXGRIDHW; i++) {
        for (j = 0; j < MAXGRIDHW; j++) {
            b->grid[i][j] = '\0';
        }
    }
}


bool uniqueChars(Node* b)
{
    int i, j, chars = 0;
    bool appears;


    for (i = 0; i < MAXGRIDHW; i++) {
        for (j = 0; j < MAXGRIDHW; j++) {
            b->grid[i][j] = toupper(b->grid[i][j]);
            if (b->grid[j] == b->grid[i]) {
              appears = true;
              break;
            }
        }
        if (!appears) {
            chars++;
        }
    }


    if (b->height < chars || b->width < chars) {
        return false;
    }
    return true;
}


void setHeightWidth(Node* b, int h, int w)
{
    b->height = h;
    b->width = w;
}

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This isn't directly related to your problem, but you can replace this:

Code:

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typedef enum bool{ false = 0, true = 1 } bool;

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with this:

Code:

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#include <stdbool.h>

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That's been a part of standard C since 1999. Welcome to (the end of) the 20th century! :)

> if (b->grid[j] == b->grid[i])
You're not comparing characters, but the (address of) the start of two arrays of characters.

Which will be of course the same if i == j

Also

Code:

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b->grid[i][j] = toupper(b->grid[i][j]);

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Is most likely a little bit suspect. You will be updating the contents of the grid and that might have a wider impact in a larger program.

Quote:

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a function that counts the number of unique characters

---

Code:

---

#include <stdio.h>
#include <string.h>

int uChars( char *string ) {
 int hasChar[256] = { 0 }, totalUC = 1;
  for ( int i=0; i<(strlen(string)-1); i++ )
    hasChar[ string[i] ] = 1 ;
  for ( int i=0; i<256; i++ )
    if ( hasChar[i] ) totalUC++;
 return totalUC;
}

int main( int args, char * argv[] ) {
  int result = uChars("testing");
  printf( "[%i] unique characters.", result );
  return 0;
}

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Quote:

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Originally Posted by Structure

a function that counts the number of unique characters

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You really need to stop this bad habit of posting code with no context, or in this case, taking it out of context by omitting "in a 2D char array". If you did want to provide context, then you should mention how a 2D array can be treated as 1D array, upon which code that handles a 1D array could be used.

Quote:

---

Originally Posted by Structure

Code:

---

#include <stdio.h>
#include <string.h>

int uChars( char *string ) {
 int hasChar[256] = { 0 }, totalUC = 1;
  for ( int i=0; i<(strlen(string)-1); i++ )
    hasChar[ string[i] ] = 1 ;
  for ( int i=0; i<256; i++ )
    if ( hasChar[i] ) totalUC++;
 return totalUC;
}

int main( int args, char * argv[] ) {
  int result = uChars("testing");
  printf( "[%i] unique characters.", result );
  return 0;
}

---

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Interesting. Are you running it on ARM?

Because on Intel you have a security issue as characters are signed, so:

Code:

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    hasChar[ string[i] ] = 1

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...will trash the stack. This could happen if somebody tries to process UTF-8 Unicode text.