根据前序和中序遍历输出二叉树

public class ReconstructionTree {

    private static class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;

        public TreeNode(int val) {
            // TODO Auto-generated constructor stub
            this.val = val;
        }
    }

    public static void main(String[] args) {
        int[] preOrder = { 1, 2, 4, 5, 7, 3, 9 };
        int[] inOrder = { 4, 2, 7, 5, 1, 9, 3 };
        ReconstructionTree resTree = new ReconstructionTree();
        TreeNode root = null;
        root = resTree.buildBinaryTree(preOrder, 0, inOrder, 0,
                inOrder.length - 1, root);
        System.out.println("前续遍历");
        resTree.preOrderTree(root);
        System.out.println("中序遍历");
        resTree.inOrderTree(root);
    }

    public void preOrderTree(TreeNode root){
        if(root!=null){
            System.out.print(root.val+"  ");
            preOrderTree(root.left);
            preOrderTree(root.right);
        }
    }
    public void inOrderTree(TreeNode root){
        if(root!=null){
            inOrderTree(root.left);
            System.out.print(root.val+"  ");
            inOrderTree(root.right);
        }
    }
    private TreeNode buildBinaryTree(int[] preOrder, int index, int[] inOrder,
            int beg, int end, TreeNode root) {
        // TODO Auto-generated method stub
        if (index >= preOrder.length)
            return null;
        
        int i;
        System.out.println("*"+preOrder[index]+"*  beg:"+beg+" end:"+end+"  index:"+index);
        
        for (i = 0; i < inOrder.length; i++) {
            if (inOrder[i] == preOrder[index]) {
                break;
            }
        }
        if(i<beg||i>end)
            return null;
        root = new TreeNode(preOrder[index]);
        System.out.println("i:"+i);
        if (i < inOrder.length) {
            if (i <= beg)
                root.left = null;
            else {
                root.left = buildBinaryTree(preOrder, index + 1, inOrder, beg,
                        i - 1, root.left);
            }
            if (i >=end) {
                root.right = null;
            } else {
                root.right = buildBinaryTree(preOrder, i - beg + index + 1,
                        inOrder, i + 1, end, root.right);
            }
        }
        return root;
    }
}