Problem with comparing strings!

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  1. #1
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    Feb 2009
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    Problem with comparing strings!

    I have a problem with comparing strings.
    What i need is to write a program that reads a file input with numbers and strings, and put the numbers in one array x[] and the characters in another one y[] (characters with only one letter), and then compare the characters. But the comparing process does not work, and i do not know why. I am realy stuck in here.
    Here is the code:

    Code:
    #include <stdio.h>
    #include <string.h>
    
    #define MAX 100
    #define N "N"
    
    void main()
    {
    unsigned int max, min;
    int x[MAX];
    char y[MAX], z[MAX], buf[3];
    FILE *file;
    int i, j;
    
    file = fopen("SPRATOVI.IN", "rt");
    
    fscanf(file, "%d", &j);
    max = 0;
    min = 0;
    for(i = 0;i < j;i++)
    {
    fscanf(file, "%d %c%c", &x[i], &y[i], &z[i]);
    printf("%d %c\n", x[i], y[i]);
    }
    for(i = 0;i < j;i++) 
    {
    if(strcmp(y[i], N) == 0)
    {
    if(x[i] > max)
    {
    max = x[i];
    }
    }
    else {
    if(x[i] < min)
    {
    min = x[i];
    }
    }
    
    }
    return;
    }
    The first for loop with the printf() is fine - i get the numbers and chars on screen.
    There is a problem with the second one, i.e. the strcmp() function, and i get just segmentation fault error. I have tried different methods for doing this, but no success.

    Please somebody help,
    Thank you.

  2. #2
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  3. #3
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    I don't quite get the format of your programs I/O handling, tell me if I've got it right here. The first line in the .in file is the number of proceeding lines. An integer and two chars situate themselves on a single line, awaiting their respective entry into an array. (Side note: Why the second char? Though you put it in an array, you never bring attention to it ever again). If the char value is N, then the corresponding integer value is compared with the present min and max values. Respective replacements occur.

    If this is correct, then you do not need to use strcmp - you can directly compare two char values. See the program below.

    Code:
    #include <stdio.h>
    
    #define MAX 100
    #define N 'N'
    
    int main()
    {	
    	FILE 	*f;
    	int	x = 0, j, max, min, integers[MAX];
    	char	characters[MAX];
    	
    	/* Try opening the file */
    	if ((f = fopen("derp.in", "r")) == NULL)
    	{
    		printf("Sorry, could not open that file\n");
    		exit(1);
    	}
    	
    	/* Get first number (which I assume is the number of following lines) */
    	fscanf(f, "%d", &j);
    
    	/* get contents of the file */
    	for (x = 0; x < j; x++) 
    		fscanf(f, "%d %c", &integers[x], &characters[x]);
    
    	/* Set the min/max to be the first element in the array */
    
    	max = integers[0];
    	min = integers[0];
    
    	/* compare the characters */
    	for (x = 0; x < MAX; x++)
    	{
    		if (characters[x] == N)
    		{
    			if (integers[x] < min)
    				min = integers[x];
    			else if (integers[x] > max)
    				max = integers[x];
    		}	
    	}
    
    	printf("Max value: %d\n", max);
    	printf("Min value: %d\n", min);
    	return 0;
    }

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