下三角矩阵

/*
 * 下三角矩阵的测试函数
 * lowerTriangularMatrix.cpp
*/
#include<iostream>
#include"lowertriangularmatrix.h"

using namespace std;

int main(void)
{
    lowerTriangularMatrix<int> x(20);
    x.set(1,1,22);
    x.set(5,3,44);
    x.set(8,5,0);
    x.set(10,2,55);
    x.set(8,5,0);

    cout << x.get(10,2) << endl;
    cout << x.get(5,3) << endl;
    cout << x.get(1,1) << endl;
    cout << x.get(10,14) << endl;
    cout << x.get(8,5) << endl;

    return 0;
}

/*
 * 下三角矩阵的类定义
 * lowerTriangularMatrix.h
*/
#ifndef LOWERTRIANGULARMATRIX_H
#define LOWERTRIANGULARMATRIX_H

#include"myexceptions.h"
using namespace std;

template<class T>
class lowerTriangularMatrix
{
  public:
    //构造函数和析构函数
    lowerTriangularMatrix(int theN = 10);
    ~lowerTriangularMatrix(){delete [] element;}

    T get(int,int) const;//获取矩阵中元素
    void set(int,int,const T&);//设置矩阵元素值
private:
    int n;//矩阵非零元素最大个数
    T *element;//矩阵中元素存储所在数组
};

//构造函数
template<class T>
lowerTriangularMatrix<T>::lowerTriangularMatrix(int theN)
{
    if(theN < 1)
        throw illegalParameterValue("Matrix size must be > 0");

    n = theN;
    element = new T [n*(n + 1)/2];
}


//get()函数的实现
template<class T>
T lowerTriangularMatrix<T>::get(int i, int j) const
{
    if(i < 1 || j < 1 || i > n || j > n)
        throw matrixIndexOutOfBounds();

    if( i >= j)
        //矩阵非零元素按照行主映射方式，第一行元素个数为1，第二行为2，……，第i行为i
        //所以元素在数组中的顺序应该为i*(i-1)/2+j-1
        return element[i*(i - 1)/2+j-1];
    else
        return 0;
}


//set()函数的实现
template<class T>
void lowerTriangularMatrix<T>::set(int i, int j, const T& newValue)
{
    if(i < 1 || j < 1 || i > n || j > n)
        throw matrixIndexOutOfBounds();

    if(i >= j)
        element[i*(i-1)/2+j-1] = newValue;
    else
        if(newValue != 0)
            throw illegalParameterValue
                ("elements not in lower triangle must be zero");
}

#endif // LOWERTRIANGULARMATRIX_H

/*
 * 异常类
 * myExceptions.h
*/

#ifndef MYEXCEPTIONS_H
#define MYEXCEPTIONS_H
#include<string>

using namespace std;

class illegalParameterValue
{
  public:
    illegalParameterValue(string theMessage = "Illegal parameter value")
    {
        message = theMessage;
    }
    void outputMessage()
    {
        cout<<message<<endl;
    }
private:
    string message;
};

class matrixIndexOutOfBounds
{
public:
    matrixIndexOutOfBounds
    (string theMessage = "Matrix index out of bounds")
    {
        message = theMessage;
    }
    void outputMessage()
    {
        cout << message <<endl;
    }
private:
    string message;
};

class matrixSizeMismatch
{
  public:
    matrixSizeMismatch(string theMessage =
            "The size of the two matrics doesn't match")
    {
        message = theMessage;
    }
    void outputMessage()
    {
        cout << message <<endl;
    }
private:
    string message;
};

#endif // MYEXCEPTIONS_H