main.c

 char* getHint(char* secret, char* guess) { 
    int lenght = strlen(secret);
    if(lenght != strlen(guess))
        return NULL;
    unsigned int x = 0,y = 0;
    int cow = 0,bull = 0;
    bool* val = (bool*)calloc(false, lenght * sizeof(bool));
    while(x < lenght){
        if(guess[x] == secret[x])
            bull++;
        else{
            y = 0;
            while(y < lenght){
                if(guess[y] == secret[x] && val[y] == false){
                    val[y] = true;
                    cow++;
                    break;
                }
                y++;
            }
        }
        x++;
    }
    char* res = (char*)malloc(200 * sizeof(char));
    sprintf(res, "%dA%dB\0", bull, cow);
    return res;
}