Question

The program that I want achieve here is to construct a tree by hard coding, and then print out the hard code tree. I start with a struct which contain a object name, a question, and a yes or no node that point to the same struct. In the main method, i tried to construct the struct step by step. But I believe that is not the right way of creating a tree with node.

Description of my design: It s a game between computer and user, the computer ask for the question, and then the user answer it with yes or no, and the computer will guess for the object.

                  Start here
                       |
                       v
              Does it have a tail?
             /yes               no\
            v                      v
       a pangolin         Is it flat, round and edible?
                              /yes               no\
                             v                      v
                        a pizza                    Pete




#include <stdio.h>
#include <stdlib.h>
//object name as key, questions as value
struct node {
  char *objectname;// a string declaration to hold an object-name (which may be NULL)
  char *question;// a string declaration to hold a question (which may be NULL)
  struct node *yes_ptr; // only NULL for objects
  struct node *no_ptr; // only NULL for objects

};

typedef struct node thenode;

thenode *objectname = NULL;
thenode *question =NULL;

void nodePrint(struct node *ptr){

if(ptr->objectname == NULL)
{
    printf("Object : [NOTHING]" );
    printf("Question : %s", ptr->question);
    printf("Yes : &s", ptr->yes_ptr);
    printf("No : &s", ptr->no_ptr);

}else {
    printf("Object : %s", ptr->objectname);
    printf("Question : [NOTHING]");
}
}

int main(argc, **argv){
//if ((new_obj = malloc(sizeof(thenode))) == NULL) { abort(); }

thenode a={NULL, "Does it have a tail?", "a pangolin", "pete"};
thenode b={"a pizza",NULL, NULL, NULL};
//thenode c={NULL, "Is it flat, round and edible?", "a pizza", "pete"};
//thenode c={NULL, "Can you dip it in your tea? ", "biscuit", "a pizza"};
struct node *ptr = &thenode;
nodePrint(&a);
nodePrint(&b);

}

Answer 1

You can put the “constant” data in an array, including pointers.

thenode thenodes[] =
/* 0 */ {{ NULL, "Does it have a tail?", thenodes+1,thenodes+2}
/* 1 */ ,{ "a pangolin", NULL,NULL,NULL}
/* 2 */ ,{ NULL, "Is it flat, round and edible?", thenodes+3 , thenodes+4 }
/* 3 */ ,{"a pizza",NULL, NULL, NULL}
/* 4 */ ,{ "pete", NULL,NULL,NULL}
        };

void nodePrint(struct node *ptr){

if (!ptr) return;
    printf("{" );
if (ptr->objectname == NULL) {
    printf("Object : [NOTHING]" );
    printf("Question : %s", ptr->question);
    printf("Yes : " ); nodePrint(ptr->yes_ptr);
    printf("No : "); nodePrint(ptr->no_ptr);

    }else {
    printf("Object : %s", ptr->objectname);
    printf("Question : [NOTHING]");
    }
    printf("}" );
}

int main(int argc, char **argv){
struct node *ptr = thenodes;

nodePrint(ptr);

return 0;
}