Inserting and deleting spaces in a text array using C - c

Question

I've managed to create the following output from a program:
7.86 ( 8Hm,), 6.82 ( 4Hm,),12.1 ( 1Hs,).
I want to either add a space or delete a space depending on what character I am pointing to. Would sscanf allow you to do this?
I was just wondering what would be the easiest way to insert and delete spaces in this text. For example, I want to delete a space between ( and 'num' eg 8, but provide a space between H and 'letter' eg m. So far I have code that looks something like this:
typedef struct node {
int i;
char array[SIZE];
struct node* link;
} node;
node* format(void)
{
int count = 0;
int size = list_size(data, sizeof(data)) / 4;
for (node* ptr = head; ptr != NULL; ptr = ptr->link)
{
int i;
int j;
for (i = 0, j = 0; i < sizeof(ptr->array); i++, j++)
{
if (ptr->array[0] == ' ' && count == 0)
{
count++;
j--;
}
else if (ptr->array[i] == ' ' && ptr->array[i-1] == '.')
{
j--;
ptr->array[i] = ',';
}
else if (ptr->array[i] == ',' && ptr->array[i-1] == ')')
{
if (count == size)
{
ptr->array[i] = '.';
}
}
ptr->array[j] = ptr->array[i];
}
count++;
}
return head;
}
Note that the above is currently a linked list of size 3, whereby I created the latter to enable swapping of "groups" of characters and then reverse the order in a specific way. Would it be easier to format if I passed everything back to a single array first?
Any tips/advice would be gratefully received!

Answer 1

The easiest way is to use sscanf to parse correctly the string and then just print it to another string. Manually parsing the string in the way you are doing it will give you no observable speed/memory gain and will just add a ton of code.
Example
#include<stdio.h>
int main(){
char str[]= "7.86 ( 8Hm,), 6.82 ( 4Hm,),12.1 ( 1Hs,).";
float f1, f2, f3;
int i1, i2, i3;
sscanf(str, "%f ( %dHm,), %f ( %dHm,),%f ( %dHs,).", &f1, &i1, &f2, &i2, &f3, &i3);
printf("%f ( %dHm,), %f ( %dHm,),%f ( %dHs,).\n", f1, i1, f2, i2, f3, i3);
return 0;
}
scanf functions are powerful and as you can see you can use them to parse your formated string. When you run the code in this example, it prints this:
7.860000 ( 8Hm,), 6.820000 ( 4Hm,),12.100000 ( 1Hs,).
The way it works is that scanf can ignore characters. So it reads the first float and then ignores blank spaces, ignores a parenthesis, reads an int, ignores Hm and so on.
My printf is formating the string the same way it came from the input. You can tweak it to meet your requirements. You should also search around and limit decimal digits. But the basic idea is that you get the data you need from the string and then you can print that data the way you want.

Answer 2

Doing the best to understand what you currently have in ptr-array and then how to accomplish the reformat, which you appear to want to do in-place simply updating ptr->array to hold to updated formatted string, then you can build a correctly formatted buffer to replace the current ptr->array.
Note: the better solution would be separate the values in ptr->array into actual separate values and hold that as part of your linked list where you either statically declare an array of structs to hold your values and units (which is my best guess for 7.86 (8Hm,). That would allow you to format the values in any way needed rather than being stuck with what is in array. For example:
#define USIZE 8
typedef struct values {
double value;
char[USIZE];
} values;
typedef struct node {
int i;
char array[SIZE];
values *vals;
struct node* link;
} node;
or, e.g.:
typedef struct node {
int i;
char array[SIZE];
values vals[3];
struct node* link;
} node;
Regardless, your original question was how to reformat your existing ptr->array removing spaces following '(' and separating '8Hm' to '8H m' in your sample data of:
7.86 ( 8Hm,), 6.82 ( 4Hm,),12.1 ( 1Hs,).
Given that you are iterating over each node in your list, this reformat would presumably only be run once after you have collected/stored all your nodes. One approach is to construct a new buffer holding array in its new format and then replace your new array with the properly formatted buffer.
Yes, there are many ways to do this, but if your reformat criteria is limited, simply walking down array with a pointer using the tried and true inch-worm method filling your new buffer with the characters in the desired format is about as easy and flexible as anything else.
Below, the example creates a new buffer (buf[SIZE]) copies/replaces/removes characters from ptr->array and then replaces ptr->array with the contents of buf.
NOTE: I have not run this on any data, so you may need to tweak the logic a bit. This is merely meant to show you an approach that can be used and to make that as close a possible to a solution to your question (to the best I understood it).
NOTE2: you can replace the upper/lower case conditionals below with isupper or islower from ctype.h if you are not limited to specific headers. Additionally, memcpy below will require string.h, but can be re-written to simply do the copy without it if that is an issue.
node* format(void)
{
/* for each node in list */
for (node* ptr = head; ptr != NULL; ptr = ptr->link)
{
/* declare a pointer to `ptr->array` and `buf` */
char *p = ptr->array;
char *pend = p + SIZE;
char buf[SIZE] = {0};
char *bp = buf;
/* for each char in ptr->array */
while (p < pend)
{
/* if not the first char */
if (p > ptr->array)
{
/* if current char is ' ' */
if (*p == ' ')
{
/* if previous char is one of the following */
if (*(p - 1) == '.') *bp++ = ',';
if (*(p - 1) == ')') *bp++ = '.';
if (*(p - 1) == '(') { p++; continue; } /* remove ' ' after '(' */
}
/* if current is lower case & prior is upper, separate */
else if (('a' <= *(p - 1) && *(p - 1) <= 'z') && ('A' <= *p && *p <= 'Z'))
{
*bp++ = ' ';
*bp++ = *p;
}
/* default - copy current to buf */
else
*bp++ = *p;
}
p++; /* advance to next char */
}
/* copy formatted string to ptr->array */
memcpy (ptr->array, buf, SIZE);
}
return head;
}
Note3: if SIZE is a global #define, then replace sizeof (ptr->array) wtih SIZE.