[C]How to compare two strings w/o using strcmp()

kponenation · 11-22-2005, 01:39 AM

The followings are my code

Code:

int i = 0;
     int tmpArray;
     int result;
     while (i < N-1){
           result = compare_words(word_array[i], word_array[i+1]);
           printf("%d",result);
           if (result = 0){
                 tmpArray = *word_array[i];
                 *word_array[i] = *word_array[i+1];
                 *word_array[i+1] = tmpArray;
                  }           
     i = i + 1;      
           }

result =0 means word_array[i] >word_array[i+1]

how can i make this to work?

Thanks in advance.

primo · 11-22-2005, 02:00 AM

There's no primitive to do it in C as it's done by other languages. If there's a need to skip strcmp(), you should do it manually then.

kponenation · 11-22-2005, 02:03 AM

i figured out the comparing part ....
i need to know how to sort the words now...
i think my algorithm is correct (i already wrote this in Java)
but it doesn't work.

Wim Sturkenboom · 11-22-2005, 05:12 AM

What immediately catches the eye:

Code:

if (result = 0)

This is not a compare but an assign (so result will be set to zero)

dmail · 11-22-2005, 07:42 AM

Quote:

Originally posted by kponenation
The followings are my code

Code:

int i = 0; int tmpArray; int result; while (i < N-1){ result = compare_words(word_array[i], word_array[i+1]); printf("%d",result); if (result = 0){ tmpArray = *word_array[i]; *word_array[i] = *word_array[i+1]; *word_array[i+1] = tmpArray; } i = i + 1; }

result =0 means word_array[i] >word_array[i+1]

how can i make this to work?

Thanks in advance.

does this code really compile?

by the looks of the code word_array is an array of pointers to strings, is this correct?
but then this line confuses me

Code:

tmpArray = *word_array[i];

if word_array is an array of strings
then word_array[i] is a pointer to a string, then dereferencing it gives the first char in the array, and you put this in an int(which is the same size as a char);
it looks like you are trying to sort strings(whole words) but then you do

Code:

                 *word_array[i] = *word_array[i+1];
                 *word_array[i+1] = tmpArray;

maybe ive lost the plot, but maybe you could give some more info like what you are exactly are trying to do and include the declartion of the types.

kponenation · 11-22-2005, 09:49 AM

Thanks for your reply.
i'll just post the function sort()

Code:

int sort_words(char **word_array, int N ){   
     int i = 0;
     int tmpArray;
     int result;
     while (i < N-1){
           result = compare_words(word_array[i], word_array[i+1]);
           printf("%d",result);
           if (result = 0){
                 tmpArray = *word_array[i];
                 *word_array[i] = *word_array[i+1];
                 *word_array[i+1] = tmpArray;
                                   }           
     i = i + 1;      
           }
     return 0;
}

Above code did compile w/o any warnings or errors. word_array is a double pointer to a two dimentional array.
Thank you.

Wim Sturkenboom · 11-22-2005, 10:12 AM

as I said:
if(result = 0)
will assign 0 to result

and this will always evaluate to false and you will never do the swap

There might, btw, be a couple of other things wrong (did not look at it).

kponenation · 11-22-2005, 10:17 AM

thanks Wim,
so i changed it to result ==0
but now it won't even go into the while loop...

kponenation · 11-22-2005, 10:46 AM

I modified my code a little

Code:

int sort(char **word_array, int N){   
     int i = 0;
     int j = 0;
     int tmpArray;
     int result;
     while (i < N){
           while(j < N-1){
           result = compare_words(word_array[j], word_array[j+1]);
           printf("%d",result);
           if (result == 0){
                 tmpArray = *word_array[j];
                 *word_array[j] = *word_array[j+1];
                 *word_array[j+1] = tmpArray;
                 }
                 j = j +1;
                                  }           
     i = i + 1;      
           }
     return 0;
}

dmail · 11-22-2005, 11:19 AM

Quote:

Originally posted by kponenation
I modified my code a little

Code:

int sort(char **word_array, int N) { int i = 0; int j = 0; int tmpArray; int result; while (i < N) { while(j < N-1) { result = compare_words(word_array[j], word_array[j+1]); printf("%d",result); if (result == 0) { tmpArray = *word_array[j]; *word_array[j] = *word_array[j+1]; *word_array[j+1] = tmpArray; } j = j +1; } i = i + 1; } return 0; }

ok i see what you are trying to do, but thes lines still confuse me.

Code:

                   tmpArray = *word_array[j];
                  *word_array[j] = *word_array[j+1];
                  *word_array[j+1] = tmpArray;

after the first line what do you think the value of tmpArray is?
why do you have two while loops? j is never reset so if the inner loop takes j to its max value the inner loop is exited and i is incremented but j is still its max value so the inner loop is not entered.
why does the func return and int?

kponenation · 11-22-2005, 11:25 AM

value of tmpArray is the address of word_array[j] right?
word_array[0] = program
word_array[1] = linux
so word_array[0][0] = p
word_array[0][1]= r
word_array[1][0]= l
word_array[1][2]= n
returning int doesn't really matter. i just need to re-arrange (sort) the array and save it.
When i run my program it stops after tmpArray = *word_array[j];
it won't run *word_array[j] = *word_array[j+1];
Why is that?
Thanks.

dmail · 11-22-2005, 11:32 AM

Quote:

value of tmpArray is the address of word_array[j] right?

i'll have to write a small test programme to validate this, but you are trying to store a hex address in an int, which is then cast to a char? this just looks very wrong to me and i would be very suprised if you get the outcome you wanted.

kponenation · 11-22-2005, 11:40 AM

then how can i get the result i want?
thanks.

dmail · 11-22-2005, 11:54 AM

Code:

	char* words[20];
	words[0]="program\0";
	words[1]="linux\0";
	//print before we swap;
	printf("word one:%s\n word two:%s\n",words[0],words[1]);
	//swap program and linux aroung
	char* temp;
	temp = words[0];
	words[0] = words[1];
	words[1] = temp;
	//print after we swap;
	printf("word one:%s\n word two:%s",words[0],words[1]);

kponenation · 11-22-2005, 12:06 PM

yeah... but the problem is i need to make the array two dimensional because i first need to compare the two strings (each character) to see which one comes before.
so i can't do it like what you did.