C++类实现三维数组算法

在学习北京大学教授的《程序设计实习 / Practice on Programming》中，遇到了一个习题，花了很长时间研究，现在分享出来：

课题地址：https://class.coursera.org/pkupop-001/human_grading/view/courses/972168/assessments/9/submissions

课题描述：

实现一个三维数组模版CArray3D，可以用来生成元素为任意类型变量的三维数组，使得下面程序输出结果是：

0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,

30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56

,57,58,59,

注意，只能写一个类模版，不能写多个

int main()
{
	CArray3D<int> a(3,4,5);
	int No = 0;
	for( int i = 0; i < 3; ++ i )
		for( int j = 0; j < 4; ++j )
			for( int k = 0; k < 5; ++k )
				a[i][j][k] = No ++;
	for( int i = 0; i < 3; ++ i )
		for( int j = 0; j < 4; ++j )
			for( int k = 0; k < 5; ++k )
				cout << a[i][j][k] << ",";
	return 0;
}

提示：类里面可以定义类，类模版里面也可以定理类模版。例如：
class A
{
	class B {
	};
};
template <class T>
class S
{
	T x;
	class K {
		T a;
	};
};

课题实现代码：

难点：用set函数实现赋值（开始一直用构造函数实现，需要定义指针的指针）

#include <iostream>
using namespace std;

template <class T>
class CArray3D {
	template <class T>
	class CArray2D {
		template <class T>
		class CArray1D {
		public:
			CArray1D():p(NULL){}
			void set(T a)
			{
				p = new T[a];
				_a = a;
			}
			inline T& operator[]( long elem ) const
			{
				//	assert( elem >= 0 && elem < _a );
				return p[elem];
			} 

			~CArray1D()
			{
				delete[] p;
			};

		private:
			T* p;
			T _a;
		};
		public:
			CArray2D():p(NULL){}
			void set(T a, T b){
				p = new CArray1D<T>[a];
				for(int i=0; i<a; i++){
					p[i].set(b);
				}
				_b = b;
			}

			inline CArray1D<T>& operator[]( long elem ) const
			{
				//	assert( elem >= 0 && elem < _b );
				return p[elem];
			} 

			~CArray2D()
			{
				delete[] p;
			}

		private:
			CArray1D<T>* p;
			T _b;
	};

public:
	CArray3D(T a, T b, T c){
		p = new CArray2D<T>[a];
		for(int i=0; i<a; i++){
			p[i].set(b, c);
		}
		_c = c;
	}

	inline CArray2D<T>& operator[]( long elem ) const
	{
		//	assert( elem >= 0 && elem < _c );
		return p[elem];
	} 

	~CArray3D()
	{
		delete[] p;
	}

private:
	CArray2D<T>* p;
	T _c;
};

int main()

{

	CArray3D<int> a(3,4,5);

	int No = 0;

	for( int i = 0; i < 3; ++ i )

		for( int j = 0; j < 4; ++j )

			for( int k = 0; k < 5; ++k )

				a[i][j][k] = No ++;

	for( int i = 0; i < 3; ++ i )

		for( int j = 0; j < 4; ++j )

			for( int k = 0; k < 5; ++k )

				cout << a[i][j][k] << ",";

	return 0;

}