error: expression cannot be used as a function int rheight = r.height();

This error occurs when you try to use a class member function as if it were a regular function. In this case, it looks like you are trying to call a member function named "height()" on an object named "r", but you are using parentheses like you would with a regular function call.

To fix this error, you need to remove the parentheses and use the member function syntax to call the "height" function on the "r" object, like this:

int rheight = r.height;

相关问题

用Java实现分层二叉树

分层二叉树是一种特殊的二叉树，每层节点数都是2的幂次方。以下是用Java实现分层二叉树的代码：

class Node {
    int val;
    Node left, right;
    
    public Node(int val) {
        this.val = val;
        this.left = null;
        this.right = null;
    }
}

class LayeredBinaryTree {
    Node root;
    
    public LayeredBinaryTree() {
        root = null;
    }
    
    public void insert(int val) {
        if (root == null) {
            root = new Node(val);
            return;
        }
        Node curr = root;
        while (curr.left != null && curr.right != null) {
            if (val <= curr.val) {
                curr = curr.left;
            } else {
                curr = curr.right;
            }
        }
        if (val <= curr.val) {
            curr.left = new Node(val);
        } else {
            curr.right = new Node(val);
        }
    }
    
    public void printLevelOrder() {
        int h = height(root);
        for (int i = 1; i <= h; i++) {
            printLevel(root, i);
            System.out.println();
        }
    }
    
    public int height(Node node) {
        if (node == null) {
            return 0;
        } else {
            int lheight = height(node.left);
            int rheight = height(node.right);
            return Math.max(lheight, rheight) + 1;
        }
    }
    
    public void printLevel(Node node, int level) {
        if (node == null) {
            return;
        }
        if (level == 1) {
            System.out.print(node.val + " ");
        } else if (level > 1) {
            printLevel(node.left, level - 1);
            printLevel(node.right, level - 1);
        }
    }
}

这里定义了一个Node类和LayeredBinaryTree类，Node类表示树中的节点，LayeredBinaryTree类表示分层二叉树。insert方法用于插入节点，printLevelOrder方法用于按层遍历并打印分层二叉树，height方法用于计算分层二叉树的高度，printLevel方法用于打印某一层的节点。

18923 二叉树的直径

二叉树的直径是指任意两个节点间最长路径的长度。可以使用递归的思想来解决这个问题，具体的做法是：

1. 对于当前节点，计算经过该节点的最长路径长度，即左子树高度+右子树高度。
2. 分别递归左右子树，得到左右子树的最长路径长度。
3. 取三者中的最大值作为当前节点的最长路径长度。
4. 递归处理所有节点，计算出直径。

下面是基于上述思路的 C++ 代码实现：

struct TreeNode {
    int val;
    TreeNode* left;
    TreeNode* right;
    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
};

int diameterOfBinaryTree(TreeNode* root) {
    if (!root) return 0;
    int lHeight = height(root->left);
    int rHeight = height(root->right);
    int lDiameter = diameterOfBinaryTree(root->left);
    int rDiameter = diameterOfBinaryTree(root->right);
    return max(lHeight + rHeight, max(lDiameter, rDiameter));
}

int height(TreeNode* node) {
    if (!node) return 0;
    return 1 + max(height(node->left), height(node->right));
}

其中，diameterOfBinaryTree 函数用于计算二叉树的直径，height 函数用于计算二叉树的高度。