K&R Exe. 1-23 : Some Complications - c

Question

"Exercise 1-23. Write a program to remove all comments from a C program.
Don't forget to handle quoted strings and character constants
properly. C comments do not nest." K&R pg.34
Basically, I have two questions:
1)I'm completely new coding and I wanted to know if I'm at least thinking the problem the right way.
2)The code was built to ignore // till \n or /* till */. But whit the /* comment it always leaves one /.
Input: abc/*comment*/123
Output: abc/123
Input: abc/*123
Output: abc/
#include <stdio.h>
char s[1000]; //Principal array
int countS; //Number of char in array
int deletSingleLineComments(void);
int deletMultiLineComments(void);
int main(void){
int c;
while((c=getchar())!=EOF){
s[countS]=c;
++countS;
}
deletMultiLineComments(); //Function 1
deletSingleLineComments(); //Function 2
printf("\ns[]=\n%s\n\ncountS[]=%d\n",s,countS);
}
//Functions 1
int deletMultiLineComments(void){
char t[1000];
int i=0;
int inComment=0;
int diff=0;
int a,b,c;
while(i<=countS){
t[i]=s[i];
++i;
}
i=0;
while(i<=countS){
if(t[i]=='/' && t[i+1]=='*'){
inComment=1;
}
if(inComment==1){
++diff; //to equilibrate the number
}
if(inComment==0){
s[i-diff]=t[i];
}
if(t[i]=='*' && t[i+1]=='/'){
inComment=0;
}
++i;
}
s[i-diff+1]='\0';
countS=i-diff;
printf("\nt[]=\n%s\n",t);
}
//Function 2
int deletSingleLineComments(void){
int i=0;
char t[1000];
int inComment=0;
int diff=0;
while(i<=countS){
t[i]=s[i];
++i;
}
i=0;
while(i<=countS){
if(t[i] == '/' && t[i+1] == '/'){
inComment=1;
}
if(t[i]=='\n'){
inComment=0;
}
if(inComment==1){
++diff;
}
if(inComment==0){
s[i-diff]=t[i];
}
s[i-diff+1]='\0';
++i;
}
countS=i-diff;
}
Thank you.

Answer 1

while(i<=countS){ t[i]=s[i];... }
Note that character strings are zero based. For example "ABC" has length 3, it starts at zero index, and the last valid index is 2 (not 3). Therefore you should change the condition to i < string_length
while(i < countS){ t[i]=s[i];... }
Also be careful when accessing t[i+1], because while i is valid, i+1 can be out of bound.
if (i < (countS - 1))
if(t[i]=='/' && t[i+1]=='*')
In order to assign one string to another, you can introduce a second variable k, and increment k after each assignment. This method is easier (in my opinion) than using the diff variable and doing additions and subtractions.
In addition, rather than char t[1000];, you can use char *t = malloc(countS); to declare a temporary variable of length countS, then it has to be freed at the end with free(t). If your compiler supports variable length array, you can just put char t[countS].
Example:
char s[1000]; //Principal array
int countS; //Number of char in array
//Functions 1
void deletMultiLineComments(void)
{
char *t = malloc(countS);
int i = 0;
int k = 0;
int inComment = 0;
while (i < countS)
{
t[i] = s[i];
++i;
}
i = 0;
while (i < countS)
{
if (i < countS - 1)
if (t[i] == '/' && t[i + 1] == '*')
{
inComment = 1;
i+=2;
continue;
}
if (inComment == 1)
{
if (i < countS - 1)
if (t[i] == '*' && t[i + 1] == '/')
{
inComment = 0;
i+=2;
continue;
}
}
if (inComment == 0)
{
s[k] = t[i];
k++;
}
++i;
}
free(t);
s[k] = '\0';
countS = k;
printf("mulitline comment removed %s\n", s);
}
//Function 2
void deletSingleLineComments(void)
{
char *t = malloc(countS);
int i = 0;
int k = 0;
int inComment = 0;
while (i < countS)
{
t[i] = s[i];
++i;
}
i = 0;
while (i < countS)
{
if (i < countS - 1)
if (t[i] == '/' && t[i + 1] == '/')
{
inComment = 1;
i += 2;
continue;
}
if (t[i] == '\n')
{
inComment = 0;
}
if (inComment == 0)
{
s[k] = t[i];
k++;
}
i++;
}
free(t);
s[k] = '\0';
countS = k;
printf("single comment removed %s\n", s);
}
int main(void)
{
//get input
scanf("%s", s);
countS = 0;
while (s[countS]) countS++;
deletMultiLineComments(); //Function 1
deletSingleLineComments(); //Function 2
}