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cstringrecursionstrcmp

Having problems with my recursive function

I don't understand why it stops right after it reaches the line " if(strcmp(next,str2) == 0) return; "
for now I commented out the %.*s print line just so I can fully print the two strings that are being compared before it reaches the if statement so the 5 is irrelevant in my example input.

when I print the two strings "next" and "str2", the following shows
enter image description here

I can see the string "ABC DEF" is not the same as "BC DEFA" but it seems it satisfies the if statement because it stops the marquee function. When I comment out the if statement, it'll go through infinite recursion.
Maybe it is same I thought so I printed the strcmp program of the two strings
enter image description here
It shows strcmp is -1, which isn't 0

Can someone enlighten me? Maybe I am just missing something simple or is there a better way to break out of my recursion once next is equal to str2.

edit: I put in the rotate function

int main(){

    int n,i,signlength;
    char sign[100]; //max 99 letters

    //get number of cases
    scanf("%d",&n);

    //process each case
    for(i=0;i<n;i++){

        //ignore rest of line \n
        char ic;
        while ( (ic = getc(stdin)) != EOF && ic != '\n');
        //take in sign string and length of sign
        gets(sign);
        scanf("%d",&signlength);

        if(signlength >= strlen(sign))
                printf("[%-*s]\n",signlength,sign);

        if(signlength < strlen(sign)){

                printf("%s\n",sign);
                //printf("[%.*s]\n",signlength,sign);
                marquee(sign,signlength,sign);
        }

    }

    return 0;
}

char* marquee(char* str, int size, char* str2){

    char* next = rotate(str);

    printf("%s\n",next);
    //printf("[%.*s]\n",size,next);
    if(strcmp(next,str2) == 0)
        return;

        return marquee(next,size,str2);

}

void swap(char* a, char* b){

    char temp = *a;
    *a = *b;
    *b = temp;
}

void reverse(char* array, int size){
    int i;
    for(i=0;i<size/2;i++)
        swap(array + i, array + (size-i-1));
}

char* rotate(char* str){

    reverse(str +1, strlen(str) -1);
    reverse(str, strlen(str));

    return str;
}
Solution

  • Your rotate and reverse functions both operate on your character array in-place. In fact, if you look at rotate, you can see it always returns str. So when you do:

    char* next = rotate(str);

    All it's doing it rotating str in-place and then returning str. After the call, next has the same value as str, and the original contents of str are no longer available.

    If you want to preserve str, just make a copy of it. For instance, you could do:

    char* next = rotate(strdup(str));

    That will first copy str, then call rotate which will destructively modify the copy, leaving str unchanged.