Hi,

I am doing a little program who calculates the permutation of a set of

vertex.

I use the recursivity for this calcul.

My function who calculate the permutations :

void permutation(set *e, int *current, int nbre)

{

set *p, *copie;

int *tmp;

int i;

if(e != NULL)

{

p = e;

tmp = realloc(current , sizeof *current *(nbre+1));

if(tmp == NULL) exit(-1);

else current = tmp;

while(p != NULL)

{

copie = copie_elt(e); // the function copie_elt let to copy the

set e and to return this copy

current[nbre] = p->st;

delete_elt(&cop ie,p->st); // this function let to delete an

element of copie. The element who

// is associated with the value p->st

permutation(cop ie,current,nbre +1); // call of permutation with the

set reducted.

p = p->suivant;

}

}else{

// In current, we have stocked the current permutation,

so we print it

for(i=0; i<nbre; i++)

printf("%d - ",current[i]);

printf("\n");

}

}

I call it in the main with :

/* initialization of the variable e */

permutation(set ,current,0);

By executing the program, I have this on my screen (I tried to debug

with GDB) :

(gdb) run

3 - 1 - 2 - 4 -

*** glibc detected *** double free or corruption (fasttop): 0x0804a048

***

Program received signal SIGABRT, Aborted.

0x4004ea27 in raise () from /lib/tls/libc.so.6

(gdb)

So, I tried this function with a char * for the variable current, the

code gives it :

void permutation(set *e, char *current, int nbre)

{

set *p, *copie;

char *tmp;

int i;

if(e != NULL)

{

p = e;

tmp = realloc(current , sizeof *current *(nbre+1));

if(tmp == NULL) exit(-1);

else current = tmp;

while(p != NULL)

{

copie = copie_elt(e); // the function copie_elt let to copy the

set e and to return this copy

current[nbre] = p->st;

delete_elt(&cop ie,p->st); // this function let to delete an

element of copie. The element who

// is associated with the value p->st

permutation(cop ie,current,nbre +1); // call of permutation with the

set reducted.

p = p->suivant;

}

}else{

// In current, we have stocked the current permutation,

so we print it

for(i=0; i<nbre; i++)

printf("%d - ",current[i]);

printf("\n");

}

}

I call it in the main with :

permutation(e,c urrent,0);

And there, the program gives the waited answer :

(gdb) run

3 - 1 - 2 - 4 -

3 - 1 - 4 - 2 -

3 - 2 - 1 - 4 -

3 - 2 - 4 - 1 -

3 - 4 - 1 - 2 -

3 - 4 - 2 - 1 -

1 - 3 - 2 - 4 -

1 - 3 - 4 - 2 -

1 - 2 - 3 - 4 -

1 - 2 - 4 - 3 -

1 - 4 - 3 - 2 -

1 - 4 - 2 - 3 -

2 - 3 - 1 - 4 -

2 - 3 - 4 - 1 -

2 - 1 - 3 - 4 -

2 - 1 - 4 - 3 -

2 - 4 - 3 - 1 -

2 - 4 - 1 - 3 -

4 - 3 - 1 - 2 -

4 - 3 - 2 - 1 -

4 - 1 - 3 - 2 -

4 - 1 - 2 - 3 -

4 - 2 - 3 - 1 -

4 - 2 - 1 - 3 -

Program exited normally.

(gdb)

Here, the program gives all the permutations for the set = {1,2,3,4}.

It's good but the only thing that I changed between the two functions

is the int * who becam a char *.

So, I don't know what is the probleme in the first version of

permutation with the int *.

Someone would have an idea of the problem who cause this error ?

Thanks for your help.

Sylvain.