subsets filling the gaps question..

i need to complete the following structure so
it will print all the str strings in length n,that follows ththe following rules:
A.the strings have only a,b,c chars
B.a string could not have two consecutive 'a' chars
C.a sting could not have 3 consecutive 'c' chars

for example:
for n=3
it will print
aba,abb,abc,aca,acb,acc,bab,bac,bba,bbb,bbc,bca,bc b,bcc,cab,
cac,cba,cbb,cbc,cca,ccb,
and returns 21

Code:

---

#include<stdio.h>
#define N 3

int printStrings(int i, int n, char* str, int a, int c){
        int count=0;
        if (?? 1 ??) {
                printf("%s,",str);
                ?? 2 ??;
        }
       
        if (?? 3 ??) a=0;
        else{
                str[i] = 'a';
                count += ?? 4 ??;
        }
       
        ?? 5 ??;
        count += printStrings(i+1,n,str,a,c);
       
        if (c==2) ?? 6 ??;
        else{
                str[i] = 'c';
                count += ?? 7 ??;
        }
        ?? 8 ??;
}



void main(){
        char str[N+1];
        str[N] = '\0';
        printf("%d\n",printStrings(0,N,str,0,0));

}

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what each block should do

i think that each block is a given condition
for example the following block is linked with the rule that we are not allowed 3 'c' in a row
but dont know what it should do in general?

Code:

---

if (c==2) ?? 6 ??;
        else{
                str[i] = 'c';
                count += ?? 7 ??;
        }

---