Thread: Counting Frequency using linked list

My current code is now

Code:

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

typedef struct node
{
    char alpha;
    int freq;
    struct node* next;

}NODE;

int main()
{
    FILE* pInfile = NULL;
    char buffer[500];
    char string[500];

    NODE *start = NULL; //list
    NODE *temp;         //temporary node to store data
    NODE *temp2;        //for adding node
    NODE *current;      //node to traverse with
    int i = 0;
    int bCheck = 0;

    pInfile = fopen("data.txt","r");

    if(pInfile == NULL)
	{
        printf("Error: cannot open file");
	}

    while ( fgets(buffer,127,pInfile)!= NULL )
    {
        for(i = 0; buffer[i] != '\0' ; i++)
        {
            printf("%d..",i);
            buffer[i] = tolower(buffer[i]);
            printf("%c\n",buffer[i]);
            bCheck = 0;

            if(start == NULL)
            {
                start = (NODE*)malloc(sizeof(NODE));
                start->alpha = buffer[i];
                start->freq = 1;
                start->next = NULL;

                current = start;
                //start = current;
            }

            else if(start != NULL)
            {
                while(bCheck == 0)
                {
                    current = start;
                    if((isalpha(buffer[i]))||(isspace(buffer[i])))
                    {
                        printf("is alpha\n");
                        if(current->alpha == buffer[i])
                        {
                            printf("test3\n");
                            current->freq++;
                            bCheck = 1;
                        }
                        else if((current->alpha != buffer[i])&&(current->next == NULL))
                        {
                            printf("test4\n");
                            temp = (NODE*)malloc(sizeof(NODE));
                            temp->alpha = buffer[i];
                            temp->freq = 1;
                            //temp->next = NULL;

    printf("TEMP char: %c\t freq: %d\n\n",temp->alpha,temp->freq);

                            current->next = temp;
                            //temp->next = NULL;

                            /*temp2 = start;
                            while(temp2->next != NULL)
                            {
                                temp2 = temp2->next;
                            }
                            temp2->next = temp;*/

    if(temp->next==NULL)
    printf("2TEMP char: %c\t freq: %d\n\n",temp2->next->alpha,temp2->next->freq);
                            free(temp);
    current = start;
    while(current != NULL)
    {
    printf("current char: %c\t freq: %d\n\n",current->alpha,current->freq);
    current = current->next;
    }


                            bCheck = 1;
                        }
                        else
                        {
                            printf("test5\n");
                            printf("buffer[i] = %c\n",buffer[i]);
                            printf("current->alpha = %c\n",current->alpha);
                            current = current->next;
                            system("pause");
                        }
                    }
                    else
                    {
                        printf("not alpha\n");
                        break;
                    }
printf("bCheck = %d\n",bCheck);
                }

            }

        }

    }
}

My problem is in the else if part
i cannot set temp->next to null because when i set it, it crashes.
and when i don't set it and print it, it shows only the first letter and not the next letter added in
for example my text is "It seems that..."
it prints out

0..i
1..t
is alpha
test4
TEMP char: t freq: 1
current char: i freq: 1
current char: sth that is not an alphabet freq: 4788232

then the program crashes !!!

Please help me :'(

Code:

current = (NODE*)malloc(sizeof(NODE));
            current = start;

Why are you throwing away what you allocate as soon as you allocate it?


Quzah.

A bad coding policy I wanted to mention: Just ignore the while and for loops for a second and imagine what the first run through your loop looks like:

Code:

/* at the beginning of the code */
NODE *start = NULL;
 
/* ...................................... */

/*later in the code*/

current = start;

So current = NULL. First time you try to access current your program is going to explode. lol... not literally of course

It's true that you initialize start at some point but it's just bad logic to assign pointers to point to unallocated memory.

Also, stop casting malloc. There is absolutely no need to do so, if you are using standard C.

You've still got that line backwards. Assign current to start, not start to current.


Quzah.

Clean it up. No point in allocating a node that you may not use.

Code:

while input
    node = inlist( list, character )
    if node
        node->count++
    else
        list = addtolist( list, character )

There you go.


Quzah.