problem in creating a tree

This is a discussion on problem in creating a tree within the C Programming forums, part of the General Programming Boards category; Hi, I encountered some problems in creating a tree and using preorder algorithm to travel it. Code: // Create a ...

  1. #1
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    problem in creating a tree

    Hi, I encountered some problems in creating a tree and using preorder algorithm to travel it.

    Code:
    // Create a binary search tree
    
    #include<iostream>
    struct TreeNode;
    typedef struct TreeNode *PtrToNode;
    typedef struct TreeNode *Tree;
    using namespace std;
    
    struct TreeNode {
    	int data;
    	PtrToNode left;
    	PtrToNode right;
    };
    
    // insert a new node into a binary search tree
    // using a recursive algorithm
    void insert(Tree tree, int item) {
    	if( tree == 0 ) {
    		tree = (Tree)malloc(sizeof(struct TreeNode));
    		if( tree == 0 ) {
    			cout << "Fatal error!" << endl;
    			exit(1);
    		}
    		else {
    			tree->data = item;
    			tree->left = tree->right = 0;
    		}
    	}
    
    	else if( item < tree->data )
    		insert( tree->left, item);
    	else if( item > tree->data )
    		insert( tree->right, item );
    
    }
    
    // create a new binary search tree
    void createTree( Tree tree, int a[], int n ) {
    	for( int i = 0; i < n; i++ )
    		insert( tree, a[i] );
    }
    
    void preorder( Tree tree ) {
    	if( tree != 0 ) {
    		cout << tree ->data << ' ';
    		preorder( tree->left );
    		preorder( tree->right );
    	}
    }
    
    
    int main(void) {
    	const int maxsize = 5;
    	int a[maxsize] = {5,3,9,1,10};
    	Tree T = 0;
    	createTree(T,a,maxsize);
    	
    	preorder( T );
    
    	return 0;
    }
    so why there is no output to the screen??
    thanks for your help~~~

  2. #2
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    problem in creating a tree
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