Thread: Problem passing data between functions

I have tried to create a binary tree structure for storing data, but I can't seem to get the program to compile. It flags up an error when returning a from the function createtree and when assigning this result to a in the main program.

They are both data type tree which is created at the start, and both are pointers. I cannot understand why the program cannot return/assign these two values.

It is probably something very simple but I would be very grateful for the help.

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct tree{
  char thisnode[50];
  struct tree *leftnode;
  struct tree *rightnode;
}Tree;

Tree *makenode(char *in, Tree *l, Tree *r){
  Tree *t = malloc(sizeof(Tree));
  t->leftnode = l;
  t->rightnode = r;
  strncpy(t->thisnode, in, 9);
  return t;
}

Tree *insertnode(Tree *root, char *data){
  if (root == NULL) {
    root = makenode(data, NULL, NULL);}
  else if(strcmp(data, root->thisnode)<0){
    root->leftnode = insertnode(root->leftnode, data);}
  else{
    root->rightnode = insertnode(root->rightnode, data);}
  return root;
}

char *search(Tree *root, char *number){
  if (root == NULL){
    return "Not Found";}
  else if(strcmp(number, root->thisnode) == 0){
    return root->thisnode;}
  else if(strcmp(number, root->thisnode) < 0){
    return search(root->leftnode, number);}
  else {
    return search(root->rightnode, number);
  }
}

Tree createtree(){
     char i[25];
     int j;
     Tree *a = NULL;
     while (i[0] != '.'){
           for(j = 0; j < 25; j++){
                 i[j] = getchar();
                 a = insertnode(a,i);                 
           }
     }
     return a;
}

int main()
{
    Tree *a = NULL;
    a = createtree();
    
    if(a != 0) { 
    printf("\n");
    while(a->leftnode != 0) {
        printf("%s", a->thisnode);
        a = a->leftnode;
    }
    printf("%s", a->thisnode);
}
    return 0;
}

Code:

Tree createtree(){

Code:

     Tree *a = NULL;

Code:

return a;

notice anything wrong?

oh god, I can't believe I was that stupid.

Thanks a lot for the help

yeh I know thats the next problem I discovered, i've replaced the for loop with a second while loop.

Although it doesn't seem to exit this loop, Does getchar() scan newline characters in? if not thats where my next problem lies. I have included the modified function createtree below just incase it helps.

Code:

Tree createtree(){
     
     char i[50];
     int j;
     Tree *a = NULL;
     while (i[0] != '.'){
           j = 0;
           while (i[j] != '\n'){
                 i[j] = getchar();  
                 j++;              
           }
     a = insertnode(a,i); 
     }
     return *a;
}

Look the function signature, it isn't returning a Tree * as you expect.

you could use a for loop then say
ch[i] = getchar();
if ch[i] != '.' then insert
else break;
flush stdin (the correct way of course)

I think that would work. But someone else probably has a really neat way to do this. I'm sure there is one, I just can't think of it.

hmmm, I think I'm a little confused after looking over this again. each node contains a string? but your trying to insert nodes after every character you get.
is a node supposed to just contain 1 char? or a string