A simple Tree class problem.

This is a discussion on A simple Tree class problem. within the C++ Programming forums, part of the General Programming Boards category; Can someone help me finding that why this code is not working as expected? Code: #include <iostream> #include <cstdlib> using ...

  1. #1
    msp
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    Unhappy A simple Tree class problem.

    Can someone help me finding that why this code is not working as expected?
    Code:
    #include <iostream>
    #include <cstdlib>
    using namespace std;
    
    struct Node
    {
            int item;
            Node *left;
            Node *right;
    };
    
    class Tree
    {
            Node *root;
    public:
            Tree()
            {
                    root = new Node;
                    root->left = 0;
                    root->right = 0;
                    root->item = 0;
            }
    
            void insert(int i) { ins(i, root); }
            void inorder() { in(root); }
    
    private:
            void ins(int i, Node *r)
            {
                    if (!r)
                    {
                            r = new Node;
                            r->left = r->right = 0;
                            r->item = i;
                    }
                    else
                    {
                            if (r->item > i) ins(i, r->left);
                            else if (r->item < i) ins(i, r->right);
                    }
            }
            
            void in(Node *r)
            {
                    if (r)
                    {
                            in(r->left);
                            cout << r->item << ' ';
                            in(r->right);
                    }
            }
    };
    
    int main()
    {
            Tree t;
            for (int n=1; n<=10; ++n)
            {
                    t.insert(rand() % 100);
            }
            t.inorder();
            return 0;
    }

  2. #2
    chococoder
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    without knowing what you expect it to do, no.

  3. #3
    Registered User
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    You haven't modified any of your pointers to point to anything, you're just copying them around. Try passing them by reference, and see if that helps, ie
    Code:
            void ins(int i, Node* & r)
    Also, its a bit pointless creating a 'zero' node in the tree's constructor, since binary trees are recursive, all you're doing is adding an extra unnecessary jump. if the tree is empty, its better to set your root as a null pointer.
    Last edited by Bench82; 08-14-2007 at 06:56 AM.

  4. #4
    msp
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    Quote Originally Posted by jwenting View Post
    without knowing what you expect it to do, no.
    Well I just want it to insert items in tree and then print the inserted items.
    Quote Originally Posted by Bench82
    Also, its a bit pointless creating a 'zero' node in the tree's constructor
    Oops! I did not realize that. Thanks.

    Yeah I hope that reference to pointer may work. I'll test it and post.
    Thanks guys!

  5. #5
    msp
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    It works now! Thanks everyone!
    Code:
    #include <iostream>
    #include <cstdlib>
    using namespace std;
    
    struct Node
    {
            int item;
            Node *left;
            Node *right;
    };
    
    class Tree
    {
            Node *root;
    public:
            Tree()
            {
                    root = 0;
            }
    
            void insert(int i) { ins(i, &root); }
            void inorder() { in(root); }
    
    private:
            void ins(int i, Node **p)
            {
                    Node *r = *p;
                    if (!r)
                    {
                            r = new Node;
                            r->left = r->right = 0;
                            r->item = i;
                            *p = r;
                    }
                    else
                    {
                            if (r->item > i) ins(i, &r->left);
                            else if (r->item < i) ins(i, &r->right);
                    }
            }
            
            void in(Node *r)
            {
                    if (r)
                    {
                            in(r->left);
                            cout << r->item << ' ';
                            in(r->right);
                    }
            }
    };
    
    int main()
    {
            Tree t;
            for (int n=1; n<=100; ++n)
            {
                    t.insert(n);
            }
            t.inorder();
            return 0;
    }

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