Sorting words in alphabetically order C - c

Question

So my exercise is to sort words in 1D char array. My code is almost working, but it always skips the last char of the last word. Here is my code. I've added some comments to make it somehow readable. I know it's not brilliant code but I've just started with programming.
int main(void) {
char input[] = "If you are working on something that you really care about you dont have to be pushed The vision pulls you Steve Jobs";
sort_alphabetically(input);
printf("%s", input);
}
int sort_alphabetically(char tab[]) {
int j = 0, k = 0, i = 0, g = 0, f = 0, l = 0;
char tmp[1001];
char tmp2[501][1001];
while (tab[i] == ' ') // skipping leading whitespaces
i++;
for (j = i; tab[j] != '\0'; j++) {
if (tab[j] != ' ' && tab[j + 1] != '\0')
k++; // counting word length
else if (tab[j] == ' ' || tab[j + 1] == '\0' || tab[j + 1] == '\0') {
// copying word t0 2d array
for (g = k; g > 0; g--) {
tmp[l] = tab[j - g];
l++;
}
tmp[l] = 0;
strcpy(tmp2[f], tmp); // copying
f++; //words ++ in tmp2
k = 0;
l = 0;
tmp[0] = 0;
}
}
tab[0] = 0;
tmp[0] = 0;
for (j = 0; j < f; j++) {
for (i = 0; i < f - 1; i++) {
if (strcmp(tmp2[i], tmp2[i + 1]) > 0) { //sorting words in alphabeticall order
strcpy(tmp, tmp2[i]);
strcpy(tmp2[i], tmp2[i + 1]);
strcpy(tmp2[i + 1], tmp);
}
}
}
for (i = 0; i < f; i++) {
strcat(tab, tmp2[i]); // copying to tab
strcat(tab, " "); //adding spaces after each word
}
// removing whitespaces
for (i = 0; tab[i] == ' ' || tab[i] == '\t'; i++);
for (j = 0; tab[i]; i++) {
tab[j++] = tab[i];
}
tab[j] = '\0';
}
;
After running this code it cuts the s in last word (Jobs). If someone can help me with this spaghetti I would be so happy.

Answer 1

The problem was with how you were handling the null byte vs the space. In the space case, you were actually on the space when you copied the string. But in the null byte case, you were one before the null byte. This leads to an off-by-one error. You need to modify the code to avoid handling it differently for spaces and null bytes:
for (j = i; tab[j] != '\0'; j++) {
//In the space case, you are on the space, but in the \0 case
//you were one before it.
//Changed this if statement so that you always copy the string
//when you're at the last character.
if (tab[j + 1] == ' ' || tab[j + 1] == '\0') {
//k is a length, but we're using it as an index
//so we will need to adjust by one
for (g = k; g > 0; g--) {
tmp[l] = tab[j - g + 1];
l++;
}
}
else
{
k++;
}
}
I worked this out by putting print statements that showed me the value of tab[j] and the value of k at each cycle. Watching your program execute, either with print statements or a debugger, is usually the best way to diagnose these sorts of issues.

Answer 2

The problem you have is in copying characters to the tmp buffer when you reach the end of the input (tab) string; that is, when tab[j + 1] == '\0' is true. In this case, you aren't copying the last data in this the for loop:
for (g = k; g > 0; g--) {
tmp[l] = tab[j - g];
l++;
}
To fix the issue, simply change the loop's 'condition' to include when g is zero, and skip this 'iteration' when you encounter a space character:
for (g = k; g >= 0; g--) { // Make sure to include any 'last' character
if (tab[j - g] != ' ') { // ... but skip if this is a space
tmp[l] = tab[j - g];
l++;
}
}
Note also that you have a redundant test in this line:
else if (tab[j] == ' ' || tab[j + 1] == '\0' || tab[j + 1] == '\0') {
which could just as well be written without the third test (which is the same as the second), thus:
else if (tab[j] == ' ' || tab[j + 1] == '\0') {

Answer 3

Caveat: Most of the other responders have pointed out the major bugs in your code, but this has some smaller ones and some simplification.
Before doing strcat back to tab, we should do tab[0] = 0 so the initial strcat works correctly.
Doing strcat(tab," ") after the one that copies the word goes one beyond the end of tab and is, therefore, undefined behavior. It also requires an unnecessary cleanup loop to remove the extra space that should not have been there in the first place.
The initial "split into words" loop can be [greatly] simplified.
There are some standard speedups to the bubble sort
I realize that you're just starting out [and some schools actually advocate for i, j, etc], but it's better to use some [more] discriptive names
Anyway, here's a somewhat refactored version:
#include <stdio.h>
#include <string.h>
int opt_dbg;
#define dbg(_fmt...) \
if (opt_dbg) \
printf(_fmt)
void
sort_alphabetically(char tab[])
{
char tmp[1001];
char words[501][1001];
char *src;
char *dst;
char *beg;
int chr;
int wordidx;
int wordcnt;
wordidx = 0;
dst = words[wordidx];
beg = dst;
// split up string into individual words
src = tab;
for (chr = *src++; chr != 0; chr = *src++) {
switch (chr) {
case ' ':
case '\t':
// wait until we've seen a non-white char before we start a new
// word
if (dst <= beg)
break;
// finish prior word
*dst = 0;
// point to start of next word
dst = words[++wordidx];
beg = dst;
break;
default:
*dst++ = chr;
break;
}
}
// finish last word
*dst = 0;
// get number of words
wordcnt = wordidx + 1;
if (opt_dbg) {
for (wordidx = 0; wordidx < wordcnt; ++wordidx)
dbg("SPLIT: '%s'\n",words[wordidx]);
}
// in bubble sort, after a given pass, the _last_ element is guaranteed to
// be the largest, so we don't need to examine it again
for (int passlim = wordcnt - 1; passlim >= 1; --passlim) {
int swapflg = 0;
// sorting words in alphabetical order
for (wordidx = 0; wordidx < passlim; ++wordidx) {
char *lhs = words[wordidx];
char *rhs = words[wordidx + 1];
if (strcmp(lhs,rhs) > 0) {
dbg("SWAP/%d: '%s' '%s'\n",passlim,lhs,rhs);
strcpy(tmp,lhs);
strcpy(lhs,rhs);
strcpy(rhs,tmp);
swapflg = 1;
}
}
// if nothing got swapped, we can stop early (i.e. everything is in
// sort)
if (! swapflg)
break;
}
// clear out destination so [first] strcat will work
tab[0] = 0;
// copy back words into original string
// adding the space as a _prefix_ before a word eliminates the need for a
// cleanup to remove the last space
for (wordidx = 0; wordidx < wordcnt; ++wordidx) {
dbg("SORTED: '%s'\n",words[wordidx]);
// adding spaces before each word
if (wordidx > 0)
strcat(tab, " ");
// copying to tab
strcat(tab,words[wordidx]);
}
}
int
main(int argc,char **argv)
{
char input[] = "If you are working on something that you really care"
" about you dont have to be pushed The vision pulls you Steve Jobs";
--argc;
++argv;
for (; argc > 0; --argc, ++argv) {
char *cp = *argv;
if (*cp != '-')
break;
switch (cp[1]) {
case 'd':
opt_dbg = ! opt_dbg;
break;
}
}
sort_alphabetically(input);
printf("%s\n", input);
return 0;
}