二叉树的最大深度

int (TreeNode* root) {
        if (root == nullptr) {
            return 0;
        }
        int leftTree = maxDepth (root->left);
        int rightTree = maxDepth (root->right);
        
        return max (leftTree, rightTree) + 1;
        
    }

int  (TreeNode* root) {
    if (root == nullptr) {
        return 0;
    }
    queue<TreeNode*> level;
    level.push(root);
    int depth = 0;
    while (!level.empty()) {
        depth++;

        int n = level.size();

        for (int i = 0; i < n; i++) {
            TreeNode* node = level.front();
            level.pop();
            if (node->left != nullptr) {
                level.push(node->left);
            }
            if (node->right != nullptr) {
                level.push(node->right);
            }
        }
    }

    return depth;
}