Need Help with Binary Tree Functions

[Highwind7]

Hello:

I am trying to finish an assignment in my class, and I have the code all typed out with no errors that keep it from compiling, but when I run it, the functions do not seem to add values to the tree. I just want some pointers (no pun intended) on what problems I am having, so I can correct the code. Any help would be greatly appreciated!!

binaryTree.h:

struct Node
{
        int val;
        struct Node *left;
        struct Node *right;
};

int SearchTree(struct Node *start, int query);
struct AddNode(struct Node *newnode, int value);
int PrintTree(struct Node *begin);

main.c:

#include <stdio.h>
#include <stdlib.h>
#include "binaryTree.h"

int main()
{
        char decision;
        int newnum;
        int findnum;
        int firstnum;
        int i;
        struct Node *root;
        root=malloc(sizeof(struct Node));
        for(i=0; i>=0; i++)
        {
                if(i==0)
                {
                        printf("Enter the number for the beginning of the tree:");
                        scanf("&#37;d", &firstnum);
                        printf("\n");
                        root->val = firstnum;
                        root->left = NULL;
                        root->right = NULL;
                }
                printf("===========================\n");
                printf("a to add a value\n");
                printf("s to search for a value\n");
                printf("l to list all stored values\n");
                printf("e to exit program\n");
                printf("Enter your choice:");
                scanf("%c", &decision);
                if(decision == 'e' || decision == 'E')
                        return 0;
                while(decision != 'a' && decision != 's' && decision != 'l' && decision != 'A' && decision != 'S' && decision != 'L')
                {
                        printf("\nThat is not a valid choice.\n");
                        printf("===========================\n");
                        printf("a to add a value\n");
                        printf("s to search for a value\n");
                        printf("l to list all stored values\n");
                        printf("Enter your choice:");
                        scanf("%c", &decision);
                        printf("\n");
                        if(decision == 'e' || decision == 'E')
                                return 0;
                }
                if(decision == 'a' || decision == 'A')
                {
                        printf("\nEnter the value to add:");
                        scanf("%d", &newnum);
                        printf("\n");
                        AddNode(root, newnum);
                }
                if(decision == 's' || decision == 'S')
                {
                        printf("\nEnter the value to search for:");
                        scanf("%d", &findnum);
                        printf("\n");
                        SearchTree(root, findnum);
                }
                if(decision == 'l' || decision == 'L')
                        PrintTree(root);
        }
        return 0;
}

binaryTree.c:

#include <stdio.h>
#include <stdlib.h>
#include "binaryTree.h"

int SearchTree(struct Node *start, int query)
{
        if (start == NULL)
        {
                printf("%d was not found.", query);
                return(-1);
        }
        else
        {
                if (query == start->val)
                {
                        printf("%d was found.", query);
                        return(0);
                }
                else
                {
                        if (query < start->val)
                                return SearchTree(start->left, query);
                        else
                                return SearchTree(start->right, query);
                }
        }
}

struct AddNode(struct Node *newnode, int value)
{
        if (newnode == NULL)
        {
                struct Node *newnode = malloc(sizeof(struct Node));
                newnode->val = value;
                newnode->left = NULL;
                newnode->right = NULL;
                return(newnode);
        }
        else
        {
                if (value < newnode->val)
                        newnode->left = AddNode(newnode->left, value);
                else
                        newnode->right = AddNode(newnode->right, value);
                return (newnode);
        }
}

int PrintTree(struct Node *begin)
{
        if (begin == NULL)
                return 0;
        PrintTree(begin->left);
        printf("%d \n", begin->val);
        PrintTree(begin->right);
        return 0;
}

[Salem]

> scanf("%c", &decision);
All other scanf formats skip white space and newlines, %c doesn't.
If you print the decimal value (%d) of decision, you'll find it likely to be a space or a newline.

Use fgets() to read a whole line, then sscanf to extract what you need without any fear of leaving the input in an undefined state.
http://faq.cprogramming.com/cgi-bin/...&id=1043284385

Oh, and in case someone decides to tell you to use fflush(stdin), then read this first
http://faq.cprogramming.com/cgi-bin/...&id=1043284351

[Highwind7]

Okay, thanks for the input. Now I just need to figure out why the tree isn't storing any values. Again, any advice would be greatly appreciated!

[matsp]

 int AddNode(struct Node *node, int value)
{
        if (node == NULL)
        {
               struct Node *node = malloc(sizeof(struct Node));
                node->val = value;
                node->left = NULL;
                node->right = NULL;
                return 0;
...

It is DEFINITELY bad style to use the same variable name for a local variable and a parameter into the function. Surely you can come up with a better name for the variable. I'm not entirely sure this code works right, and the "node" inside the if-statement is never used again, so you've just allocated some memory that is never assigned to something "permanent" - when you leave the if-statement, "node" is lost, and the memory is left "floating" without anything referencing it.

                if (value < node->val)
                        node->left = (void *)AddNode(node->left, value);
                else
                        node->right = (void *)AddNode(node->right, value);
                return 0;

This piece is also quite broken - first of all, AddNode returns an integer, not a pointer (hence the compiler telling you off and you having to cast it - but it's wrong anyways, becuase it ALWAYS returns zero .

Assuming you returned something sensible (of the type Node * perhaps), I'm not entirely sure that it would actually do the right thing - but I'm sure the code as it stands NOW isn't working, because you are setting the pointer to null.

--
Mats

[Highwind7]

Thanks for the input! The corrections have been made in the original post. I haven't tried to compile it yet, but I still think that something is wrong. Please let me know if there are any other errors in this! Thanks!

[matsp]

Ok, so you are now returning newnode, but you are still creating a local variable with the same name as the input parameter to the function - which is at the very least bad style, even if it's not technically wrong. You could easily use the incoming parameter to assign the new malloc value.

And I agree, there's probably bugs there still. One point is that you are updating the right or left node when passing down through the tree. That's probably not a good idea.

You are also missing what kind of struct you are returning from the function, so the code won't compile - before you post code, try to compile it first (and fix any errors unless you are specifically asking about what the fix for a particular error is - of course).

--
Mats

[Highwind7]

Okay, I managed to get the code to work, thanks for all of your help!

I will be posting a new message about an assignment that I have had a lot more trouble with, so please check it out and post any advice that you have.

Thanks again!!!