How to remove spaces that are in a string sentence

Question

I am trying to write a code to remove all the leading, trailing and middle of the sentence spaces but to keep only one space between the words.

For example if the input

Answer 1

You could have two arrays and two counters. Each iteration you always increase your first counter, but only increase your second when the character is not a space. A table of it would look like this.

  Char   In-Pos  Out-Pos

   ' '      0      0
   ' '      1      0
   ' '      2      0
   ' '      3      0
   'T'      4      0
   'h'      5      1
   'i'      6      2
   's'      7      3
   ' '      8      4
   ' '      9      5
   ' '     10      5
   ' '     11      5
   'i'     12      5
   's'     13      6
   ' '     14      7
   'm'     15      8
   'y'     16      9
   ' '     17     10
   ' '     18     11
   ' '     19     11
   ' '     20     11
   ' '     21     11
   's'     22     11
   't'     23     12
   'r'     24     13
   'i'     25     14
   'n'     26     15
   'g'     27     16
   ' '     28     17
   ' '     29     18
   ' '     30     18
   ' '     31     18

Answer 2

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

char** split(const char *str, const char *delimiter, size_t *len){
    char *text, *p, *first, **array;
    int c;
    char** ret;

    *len = 0;
    text=strdup(str);//strdup not standard
    if(text==NULL) return NULL;
    for(c=0,p=text;NULL!=(p=strtok(p, delimiter));p=NULL, c++)//count item
        if(c==0) first=p; //first token top

    ret=(char**)malloc(sizeof(char*)*c+1);//+1 for NULL
    if(ret==NULL){
        free(text);
        return NULL;
    }
    //memmove?
    strcpy(text, str+(first-text));//skip until top token
    array=ret;
    for(p=text;NULL!=(p=strtok(p, delimiter));p=NULL){
        *array++=p;
    }
    *array=NULL;
    *len=c;
    return ret;
}

void free4split(char** sa){
    char **array=sa;

    if(sa!=NULL){
        free(array[0]);//for text
        free(sa);      //for array
    }
}

int main(void){
    char str[100] = "    This    is my     string    ";
    char **words;
    size_t len=0;
    int i;

    words = split(str, " \t", &len);
    *str = '\0';
    for(i = 0;i<len-1;++i){
        strcat(str, words[i]);
        strcat(str, " ");
    }
    strcat(str, words[i]);
    printf("\"%s\"\n", str);
    free4split(words);
    return 0;
}

Answer 3

You could use a string tokenizer in the first instance, and use as a delimiter a whitespace(" "). For that purpose in C you use strtok.After that you parse the output of the strtok function, and for each element, if it contains more whitespaces character, you eliminate them. Also you put each corrected element in another array. Then, all you have to do is parse the new array and add a whitespace after every element. If you fancy this idea, I can provide a code draft for you.

Answer 4

#include <stdio.h>
#include <string.h>

char* trim(char str[]){
    char *p=str;
    char *token;
    if(str == NULL) return NULL;
    if(*str == '\0') return str;

    token=strtok(str, " \t");
    if(token == NULL){
        *str = '\0';
        return str;
    }
    while(NULL!=token){
        int len;
        len = strlen(token);
        if(p != token){
            memmove(p, token, len);
        }
        p += len;
        *p++ =' ';
        token = strtok(NULL, " \t");
    }
    p[-1]='\0';

    return str;
}

int main(){
    char str[100] = "    This    is my     string    ";
    printf("\"%s\"\n", trim(str));
    return 0;
}

Answer 5

Use two pointers. The first points at the next character to read, and the second points at the location to write.

If you read two spaces in a row, don't advance the write pointer.

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Another approach you may want to consider is to use strtok with " " as a delimiter.