Thread: 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;
}

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);
}

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.

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

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.

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

Since you also get a warning about this line

Code:

scanf("%c", str2)

I would look at it more carefully.

? 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?

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.

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

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

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.

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

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.