Remove/Count spaces in a string (using the same string)

Question

I have a simple problem to solve:

Read a string, print the string without space and the number of spaces.

I could do this using 2 strings, one that will store the user string and other that will store the same string without spaces. But I would like to do this using only one string.

What I have so far:

while(str[i] != '\0'){
        if(str[i] == ' '){
            contEsp += 1;
        }else{
            strcpy(&str[i - contEsp], &str[i]);
        }
        i++;
    }

The problem:

It's not counting number of spaces.

If the user types double space or more, the program doesn't count and doesn't remove spaces.

Questions:

Whats the problem with my code?

Is it possible to do this using just one string?

Everything you wrote is correct. But you did not ***ask a question***. — abelenky, Jun 07 '13 at 13:39
@abelenky There is a problem with my code please re check, i explain the problem at the end. — Kauê Gimenes, Jun 07 '13 at 13:40
This question might be a duplicate. Check this out for a C implementation: http://stackoverflow.com/questions/122616/how-do-i-trim-leading-trailing-whitespace-in-a-standard-way — Alex Vallejo, Jun 07 '13 at 13:42
yes, it is possible to do it with one string, print char by char and count spaces... — joy, Jun 07 '13 at 13:42
I could print only the chars but i want to use the string later. — Kauê Gimenes, Jun 07 '13 at 13:45
do you want to print or to copy? do you want to count or to remove? I'm totally lost :) — haylem, Jun 07 '13 at 14:06
copy is used to replace, its replacing the space with the char, removing the char in other words. — Kauê Gimenes, Jun 07 '13 at 14:09
@undur_gongor Yesterday at the class i got this problem to solve, i solved but using 2 strings. I want to try using only 1 — Kauê Gimenes, Jun 07 '13 at 14:10

score 3 · Accepted Answer · answered Jun 07 '13 at 14:00

3

Try this code:

int i = 0, contEsp =0;

while(str[i] != '\0')
{
    str[i-contEsp] = str[i];  

    if(str[i] == ' ')
      contEsp++;
    i++;       
}

str[i-contEsp] = '\0';

printf("String: %s, Spaces = %d\n",str, contEsp);

answered Jun 07 '13 at 14:00

Subbu M

194
1
5

In while loop, we should do character copying. But you were trying with strcpy & not avoiding spaces while copying (not changing the index value). Your code doesn't take care the String termination as well. – Subbu M Jun 08 '13 at 04:55

Boris · Answer 2 · 2013-06-07T13:58:17.943

0

1) Last spaces don't be cut too. Add check and action after loop.

2) I recommend to divide notions of local space counter and global space counter.

unsigned int contEsp = 0;
unsigned int i = 0;
unsigned int localEsp = 0;

while(str[i] != '\0'){
    if(str[i] == ' '){
        contEsp += 1;
        localEsp += 1;
    }else if(contEsp) {
        strcpy(&str[i - localEsp], &str[i]);
        localEsp = 0;
        continue;
    }
    i++;
}

if ( localEsp > 0 )
    strcpy(&str[i - contEsp], &str[i]);

edited Jun 07 '13 at 13:58

answered Jun 07 '13 at 13:48

Boris

597
2
10

No need, strcopy will copy i-0 to str i, nothing will change. – Kauê Gimenes Jun 07 '13 at 13:50
"ABC " - last spaces don't be cut at all. – Boris Jun 07 '13 at 13:51

undur_gongor · Answer 3 · 2013-06-07T14:45:11.857

Since the question is tagged with "performance": your approach is copying the whole remainder string whenever a space is encountered. Although it will probably not matter in reality, this is inefficient. Just process the characters one by one, e.g.:

unsigned remove_count_spaces(char *a) {
    char *b = a;
    unsigned ct = 0;

    do {
        if (*a == ' ') ct++;
        else *b++ = *a;
    } while(*a++);

    return ct;
}

... plus checking the possible wrap-around in ct.

score 0 · Answer 4 · answered Jun 07 '13 at 13:54

char* RemoveAndCountSpaces(char* s)
{
    int contEsp = 0;
    char* x = s;
    char* org = s;

    while(*s != '\0'){
        if(*s == ' '){
            contEsp++;
        } else {
            *x = *s;
            x++;
        }
        s++;
    }
    *x = *s;

    printf("%s\nSpaces Found: %d\n", org, contEsp);
    return org;
}

chux - Reinstate Monica · Answer 5 · 2013-06-07T14:04:27.710

0

Whats the problem with my code ?
1. Count is not initialized to 0
2. strcpy(&str[i - contEsp], &str[i]); is shifting the yet-to-be-processed string and then your i is not indexing the character you think.

Its possible to do this just using one string ?
Yes - below

int CountAndBlank(char *str) {
  size_t x = 0;   /* index through un-spaced string */
  size_t i;       /* Index through original string */
  for (i = 0; str[i]; i++) {
    if (!str[i] == ' ') {
      str[x++] = str[i];
    }
  }
  str[x] = '\0';
  return i - x;  /* Spaces removed is the difference */
}

...
int Count = CountAndBlank(buf);
printf("Number of spaces removed from '%s' is %d\n", buf, Count);

edited Jun 07 '13 at 14:04

answered Jun 07 '13 at 13:54

chux - Reinstate Monica

143,097
13
135
256

i got this error:'for' loop initial declarations are only allowed in C99 mode – Kauê Gimenes Jun 07 '13 at 13:59
replace `for (size_t i = 0; str[i]; i++) {` with `size_t i = 0; for (i = 0; str[i]; i++) {`. – chux - Reinstate Monica Jun 07 '13 at 14:03

Remove/Count spaces in a string (using the same string)

5 Answers5