Comparison of string characters in C

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3

I’m trying to do an exercise that tests if there’s any white space before a string and remove if you have, but is returning the following error:

Segmentation failure (recorded core image)

I can’t understand why.

Code:

#include <stdio.h>
void removerEspacosEsquerda(char string[]) {
    int i, j, cont;
    char *string2, a;
    i = 0;
    cont = 0;
    while(string[i] != 0) {
        if(string[i] == ' ') {
            cont++;
        }
        i++;
    }
    i = 0;
    j = 0;
    printf("%d", cont);
    while(string[i] != 0) {
        if(i >= cont) {
            string2[j] = string[i];
        }
        i++;
        j++;
    }
    string = string2;
}
int main() {
    char *string;
    string = " teste";
    removerEspacosEsquerda(string);
    printf("%s", string);
}
c string

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2 answers

2

Your code is too complex and the error occurred because of this, when we simplified it the error does not even have opportunity to appear. Do not need to have 2 loops (3 for the solution of the other answer) and need not have memory allocation:

#include <stdio.h>

void removerEspacosEsquerda(char string[]) {
    int cont = 0;
    for (int i = 0; string[i] != '\0'; i++, cont++) {
        if (string[i] == ' ') cont--;
        else string[cont] = string[i];
    }
    string[cont] = '\0';
}

int main() {
    char string[] = " teste";
    removerEspacosEsquerda(string);
    printf("%s", string);
}

Behold working in the ideone. And in the repl it.. Also put on the Github for future reference.

1

Segmentation failure occurs because the "string2" pointer has not been initialized.

#include <stdio.h>
#include <stdlib.h> // para malloc e free

void removerEspacosEsquerda(char string[])
{
  int i, j, cont;
  char *string2 = malloc(strlen(string)+1), a; // <-------------
  i = 0;
  ....
  ....
  strcpy(string, string2);
  free(string2); // <-------------
} // fim removerEspacosEsquerda

Note that I haven’t analyzed whether your space removal logic is correct, I’m just solving the problem of segmentation failure.

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