class 模板 "Node" 的参数列表是 missingC/C++(441)

Question

#include <iostream>
using namespace std;
template <typename T>
// we shouln't use the template here, it will cause a bug
// "argument list for class template "Node" is missingC/C++(441)"
// to fix the bug, check "
struct Node
{
    T datum;
    Node* left;
    Node* right;
};

// REQUIRES: node represents a valid tree
// MODIFIES: cout 
// EFFECTS: Prints each element in the given tree to stanhdard out
//          with each element followed by a space
void print(const Node *tree)  {
    if(tree) {            // non-empty tree
        cout << tree->datum << " ";
        print(tree->left);
        print(tree->right);
    }
}

我是C++的初学者，我正在尝试学习基本的二叉树打印，我不知道如何修复void print(const Node *tree)中Node下的红线，我看到有人说将模板 T 转换为 int 会修复错误，但我不知道为什么会这样。

Answer 1

打印函数也应该是模板函数，C++编译器需要你告诉它打印函数中Node的具体类型。见下文：

#include <iostream>
using namespace std;

template<typename T>
struct Node
{
    T datum;
    Node* left;
    Node* right;
};

template<typename T>
void print(const Node<T>* tree) {
    if (tree == nullptr) {
        return;
    }
    print(tree->left);
    cout << tree->datum << " ";
    print(tree->right);
}

class 模板 "Node" 的参数列表是 missingC/C++(441)

argument list for class template "Node" is missingC/C++(441)

c++

templates

binary-tree