Determining number of times a character appears in an array

This is a discussion on Determining number of times a character appears in an array within the C Programming forums, part of the General Programming Boards category; Below is my program. It works but then it gives a run time check failure- stack around the variable 'str2' ...

  1. #1
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    Determining number of times a character appears in an array

    Below is my program. It works but then it gives a run time check failure- stack around the variable 'str2' was corrupted. I have no idea what the deal is. Thanks
    Code:
    #include <stdio.h>
    #include <string.h>
    int main (void)
    {
    	int k = 0;
    	int count = 0;
    	int n;
    	char *pt;
    	char *pt2;
    	char str[256];
    	char str2[1];
    	printf("Enter sentence. \n");
    	while((str[k]=getchar()) != '\n')
    		k++;
    	str[k]='\0';
    	n= k + 1;
    	pt=str;
    	printf("Enter character to find in sentence. \n");
    	scanf("%s", str2);
    	pt2=str2;
    
    	while((pt=strstr(pt, pt2)) != NULL)
    	{
    		count++;
    		pt++;
    	}
    	printf("Number of times %s occurs: %d \n",str2, count);
    	
    return 0;
    }

  2. #2
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    may that was a little confusing, heres a newer version with comments except i moved my while loop into a function. so here it is
    Code:
    #include <stdio.h>
    #include <string.h>
    int main (void)
    {
    	/*Declare and intialize variables*/
    
    	int k = 0;
    	
    	int sum;
    	int n;
    	char *pt;
    	char *pt2;
    	char str[256];
    	char str2[1];
    	int occurance(char *pt, char *pt2);
    	
    	/*Get user input and assign to first string*/
    	printf("Enter sentence. \n");
    	while((str[k]=getchar()) != '\n')
    		k++;
    	str[k]='\0';
    	n= k + 1;
    	pt=str;
    	
    	/*Get from user the character to be counted 
    	  and put in 2nd array*/
    	printf("Enter character to find in sentence. \n");
    	scanf("&#37;s", str2);
    	pt2=str2;
    	sum = occurance(pt, pt2);
    	printf("Number of times %s occurs: %d \n",str2, sum);
    	
    return 0;
    }
    /*----------------------------------
    This function counts the number of times
    a specific character occurs */
    int occurance(char *pt, char *pt2)
    {
    	/*Initialize variables*/
    	int count = 0;
    	
    	/*Count number of times character occurs*/
    	while((pt=strstr(pt, pt2)) != NULL)
    	{
    		count++;
    		pt++;
    	}
    	return (count);
    }

  3. #3
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    str2 needs to have at least 2 characters in order to contain the terminating null char. So str2[2].
    Or you could make str2 a char instead of an array and use strchr instead of strstr.

  4. #4
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    so where do i need to make changes in my program i tried on my own now it wont even work or crashes

  5. #5
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    One goal in your program should be to make it as simple and as clear, as possible. If the problem says to search for a char, then search for a char, not a string.

    Code:
    	/*Get from user the character to be counted 
    	  and put in 2nd array*/
    	printf("Enter character to find in sentence. \n");
    //change this to a char
    	scanf("%s", str2);
    
    //you don't need a ptr, at all
    	pt2=str2;
    	sum = occurance(pt, pt2);
    	printf("Number of times %s occurs: %d \n",str2, sum);
    	
    return 0;
    }
    /*----------------------------------
    This function counts the number of times
    a specific character occurs */
    int occurance(char *pt, char *pt2)  //no pointers are needed 
    //no need to build a piano
    {
    	/*Initialize variables*/
    	int count = 0;
    	
    	/*Count number of times character occurs*/
    //use strchr() instead
    	while((pt=strstr(pt, pt2)) != NULL)
    	{
    		count++;
    		pt++;
    	}
    	return (count);
    }
    And you should be good to sort the rest out.

  6. #6
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    Heres what i have now after what i think fixing it the way you tell me to.
    Code:
    #include <stdio.h>
    #include <string.h>
    
    int main (void)
    {
    	/*Declare and intialize variables*/
    	int k = 0;
    	int sum;
    	int n;
    	char str[256];
    	char str2;
    	int occurance(char str, char str2);
    	
    	/*Get user input and assign to first string*/
    	printf("Enter sentence. \n");
    	while((str[k]=getchar()) != '\n')
    		k++;
    	str[k]='\0';
    	n= k + 1;
    		
    	/*Get from user the character to be counted 
    	  and put in 2nd array*/
    	printf("Enter character to find in sentence. \n");
    	scanf("%c", str2);
    	sum = occurance(str, str2);
    	printf("Number of times %c occurs: %d \n",str2, sum);
    	
    return 0;
    }
    /*----------------------------------
    This function counts the number of times
    a specific character occurs */
    int occurance(char str, char str2)
    {
    	/*Initialize variables*/
    	int count = 0;
    	
    	/*Count number of times character occurs*/
    	while((str=strchr(str, str2)) != NULL)
    	{
    		count++;
    		str++;
    	}
    	return (count);
    }
    Last edited by belkins; 11-11-2008 at 11:29 PM.

  7. #7
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    and compiles fine but when i try to execute it i get a run time error saying str2 isnt being intialized??? does anyone know whats wrong

  8. #8
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    Since you also get a warning about this line
    Code:
    scanf("%c", str2)
    I would look at it more carefully.

  9. #9
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    ? a warning, i thought they werent a big deal. i mean i can do scanf_s but still? does scanf need to be something else?

  10. #10
    and the Hat of Guessing tabstop's Avatar
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    Since when did scanf not take a pointer?

    Edit: And it's extremely rare for warnings to not be a big deal. Yeah, whatever_s is an ignorable warning, but it's the other warning on that line that I'm talking about.

  11. #11
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    i mean its not even letting the user type in a variable to initialize str2?

  12. #12
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    ok im an idiot i forget the &str, but i modified it and it asks the user but then it crashes?

  13. #13
    and the Hat of Guessing tabstop's Avatar
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    You shouldn't be able to pass str to the function occurance, since it expects a char in the first parameter, not a char array.

  14. #14
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    ok so i modified it as
    Code:
    int occurance(char *str, char str2)
    and fixed it so now its not giving me that error but now its not returning the right number, if i need to repost what i have i can if you wanna take a look

  15. #15
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    like if the user types "The dog runs fast." and want to see how many times s occurs, it should return 2 but returns 0 instead.

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