Question

I am writing a binary search tree program and I am getting the error  
"Main.cpp:30:20: error: use of undeclared identifier 'T'  
 BiTreeNode<T> *node = new BiTreeNode<T>    (b);.

我已经使用类模板编写了2个其他程序，之前我从未遇到此错误。任何帮助将不胜感激。提前致谢！我刚刚从Eclipse切换到NetBeans。我不认为这会导致错误，但我可能错了......

//////Beginning of BiTree.h//////

#ifndef BITREE_H
#define BITREE_H
#include "BiTreeNode.h"
#include <iostream>
using namespace std;

template <class T>
class BiTree
{
    private:
        BiTreeNode<T> *root;

        //use const because when we insert the data of type T from the object,
        //we want to only read it and not change it
        void insert(const T &d, BiTreeNode<T> *ptr)
        {
            if(ptr == NULL)
            {
                //creates a new tree node with data type d and its right and 
                //left child node pointers NULL
                ptr = new BiTreeNode<T>(d, NULL, NULL);
            }

            else if(d <= ptr -> data)
            {
                insert(d, ptr -> leftChild);
            }

            else if(d >= ptr -> data)
            {
                insert(d, ptr -> rightChild);
            }
        }



    public:

      BiTree()
      {
         root = NULL;
      }

      //By adding the &, the d copies the data from the object passed as an
      //argument for the insert function in main into a new node which is then put into the tree
      //Added the const since when we take in the data in from the object passed as an object
      //for the insert function in main. We don't want to change the data, we just want to read it
      void insert(const T &d)
      {
          //d is the data type you want to send in
          insert(d, root);
      }

      //prints a tree rooted at ptr in sorted order
      void inOrder(BiTreeNode<T> *ptr, ostream & out)
      {
          if(ptr != NULL)
          {
              inOrder(ptr -> leftChild, out);
              out << ptr -> data << endl;
              inOrder(ptr -> rightChild, out);
          }
      }

      void preOrder()
      {
          cout << "printing out in pre-order" << endl;
      }

      void postOrder()
      {
         cout << "printing out in post-order" << endl;
      }

      void printTree()
      {

      }


};

 #endif /* BITREE_H */

//////End of BiTree.h//////

////// BiTreeNode.h的开头///////

#ifndef BITREENODE_H
#define BITREENODE_H
#include "BiTree.h"
#include <iostream>
using namespace std;
template <class T>
class BiTree;


template <class T>
class BiTreeNode
{
    private:
        T data;
        BiTreeNode<T> *leftChild;
        BiTreeNode<T> *rightChild;

    public: 
        BiTreeNode(T Data)
        {
            data = Data;
            leftChild = NULL;
            rightChild = NULL;

        }

        friend class BiTree<T>;
};

#endif /* BITREENODE_H */

////////End of BiTreeNode.h//////



////Start of Main.cpp/////


#include <cstdlib>
#include <iostream>
#include <vector>
#include <ctime>
#include "BiTree.h"
#include "BiTreeNode.h"
using namespace std;

int main() 
{
    srand(time(NULL));
    BiTree<int> tree;


    int a = 1 + rand() % 100;

    for(int i=0; i<a; i++)
    {   
        int b = 1 + rand() % 100;
        BiTreeNode<T> *node = new BiTreeNode<T>(b);
    }

    tree.postOrder();

    tree.preOrder();

    return 0;
}
/////End of Main.cpp//////

Answer 1

您需要在某处定义T.通过包含您的T.h文件或声明实际的类T。

正如我所看到你为T定义了一个int，你必须在行中用int替换T，如下所示：

BiTreeNode<int> *node = new BiTreeNode<int>(b);

我不知道为什么我会收到错误：“Main.cpp：30：20：错误：使用未声明的标识符'T'”

1 个答案: