Compare code in reverse each word in sentence - c

Question

I have school task. To reverse each word in sentence, so example :
Input: Fried chicken, fried duck.
Output: deirF nekcihc, deirf kcud.
So except dot and comma it's not reversed.
The first code
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int main() {
int i, n, titik = 0, coma = 0;
char s[5001];
char c[5001];
char *tok;
scanf("%[^\n]s", s);
if (s[0] == ' ')
printf(" ");
tok = strtok(s, " ");
while (tok != NULL) {
strcpy(c, tok);
n = strlen(c);
for (i = n; i >= 0; i--) {
if (c[i] == ',') {
coma = 1;
} else
if (c[i] == '.') {
titik = 1;
} else
printf("%c", c[i]);
}
if (coma) {
printf(",");
coma = 0;
} else
if (titik){
printf(".");
titik = 0;
}
tok = strtok(NULL," ");
if (tok == NULL)
printf("\n");
else
printf(" ");
}
}
Second code is
#include <stdio.h>
#include <ctype.h>
#include <string.h>
int main() {
int i, j, n, prana = 0, titik = 0, coma = 0, end = 0;
char s[5001];
scanf("%[^\n]s", s);
n = strlen(s);
for (i = 0; i <= n; i++) {
if (isspace(s[i]) || iscntrl(s[i])) {
if (iscntrl(s[i]))
end = 1;
for (j = i - 1; j >= prana; j--) {
if (s[j] == '.') {
titik = 1;
} else
if (s[j] == ',') {
coma = 1;
} else
printf("%c", s[j]);
}
prana = i + 1;
if (titik) {
titik = 0;
if (end)
printf(".");
else
printf(". ");
} else
if (coma) {
coma = 0;
if (end)
printf(",");
else
printf(", ");
} else {
if (end)
printf("");
else
printf(" ");
}
}
}
printf("\n");
return 0;
}
Why the second code is accepted in test case?, but first code is not.
I tested the result it's same. Really identical in md5 hash.

Answer 1

The output of the two codes id different, because you print the terminating null character for each token in the first code. This loop:
for (i = n; i >=0 ; i--) ...
will have i == n in its first iteration. For a C string of length n, s[n] is the terminating null. This character may not show in the console, but it is part of the output.
To fix the loop, you could start with i = n - 1, but C uses inclusive lower bounds and exclusive upper bounds, and a more idomatic loop syntax is:
i = n;
while (i-- > 0) ...
Not related to your question at hand, but your codes are rather complicated, because they rely on many assumptions: words separated by spaces; only punctuation is comma or stop; repeated punctuation marks are ignored, special case for last word.
Here's a solution that treats all chunks of alphabetic characters plus the apostrophe as words and reverses them in place:
#include <stdlib.h>
#include <stdio.h>
#include <ctype.h>
void reverse(char *str, int i, int j)
{
while (i < j) {
int c = str[--j];
str[j] = str[i];
str[i++] = c;
}
}
int main()
{
char str[512];
int begin = -1;
int i;
if (fgets(str, sizeof(str), stdin) == NULL) return -1;
for (i = 0; str[i]; i++) {
if (isalpha((unsigned char) str[i]) || str[i] == '\'') {
if (begin == -1) begin = i;
} else {
if (begin != -1) {
reverse(str, begin, i);
begin = -1;
}
}
}
printf("%s", str);
return 0;
}