c++ - 为什么我收到重新定义错误C++？

Question

来自此文件heap.h的错误。重新定义MAX_HEAP和heapclass时出错。
我一直在得到一个错误，它的重新定义，我没有看到另一个定义。还有其他原因吗？
在这里找到错误。

// *********************************************************
// Header file Heap.h for the ADT heap.
// *********************************************************

#include "Data.h"  // definition of itemClass

const int MAX_HEAP = 20;
typedef itemClass keyType;

typedef itemClass heapItemType;

class heapClass
{
public:
    heapClass();  // default constructor
    // copy constructor and destructor are
    // supplied by the compiler

    // heap operations:
    virtual bool HeapIsEmpty() const;
    // Determines whether a heap is empty.
    // Precondition: None.
    // Postcondition: Returns true if the heap is empty;
    // otherwise returns false.

    virtual void HeapInsert(const heapItemType& NewItem,
                            bool& Success);
    // Inserts an item into a heap.
    // Precondition: NewItem is the item to be inserted.
    // Postcondition: If the heap was not full, NewItem is
    // in its proper position and Success is true;
    // otherwise Success is false.

    virtual void HeapDelete(heapItemType& RootItem,
                            bool& Success);
    // Retrieves and deletes the item in the root of a heap.
    // This item has the largest search key in the heap.
    // Precondition: None.
    // Postcondition: If the heap was not empty, RootItem
    // is the retrieved item, the item is deleted from the
    // heap, and Success is true. However, if the heap was
    // empty, removal is impossible and Success is false.

protected:
    void RebuildHeap(int Root);
    // Converts the semiheap rooted at index Root
    // into a heap.

private:
    heapItemType Items[MAX_HEAP];  // array of heap items
    int          Size;             // number of heap items
};  // end class
// End of header file.


here are the other files included
main contains main

main

Data.cpp

Data.h

Heap.cpp

PQ.cpp

PQ.h

Thank you

Answer 1

应该使用“#pragma once”来防止头文件内容的多次包含。
看到:
https://msdn.microsoft.com/en-us/library/4141z1cx.aspx?f=255&MSPPError=-2147217396

另请参阅:
Is #pragma once a safe include guard?