求二叉树中最大值和最小值的差值

struct TreeNode
{
    int data;
    TreeNode *left;
    TreeNode *right;
};

int max = INIT_MAX:
int min = INIT_MIN;

int get_max(TreeNode *proot)
{

    while( proot != NULL)
    {
        if (proot->data > max)
            max = proot->data;

        if (proot->data < min)
            min = proot->data;

        if (proot->left != NULL)
            get_max(proot->left);

        if (proot->right != NULL)
            get_max(proot->right);
    }

    return max-min;
}