特殊矩阵之对称矩阵

对称矩阵的一大特点就是a[i][j] == a[j][i], 可以简单地看作是两个三角形，关于中间一条对角线对称，所以在存储矩阵时，就可以存储一部分，而另一部分可以计算得出。

#include 
#include 
using namespace std;
template<class T>
class SymmetricMatrix
{
public:
    SymmetricMatrix(int* a, size_t N)
        :_row(N)
        ,_col(N)
    {
        _pData = new T[N*(N+1)>>1];
        size_t index = 0;
        for(size_t i=0; ifor(size_t j=0; j<=i;++j)
                _pData[index++] = a[i*N+j];
        }
    }
    T& Acess(int row, int col)
    {
        if(row < col)
            std::swap(row, col);
        return _pData[row*(row+1)>>1 + col];
    }
    const T& Acess(int row, int col)const
    {
        if(row < col)
            std::swap(_pData[row], _pData[col]);
        return _pData[row*(row+1)>>1 + col];
    }
    ~SymmetricMatrix()
    {
        if(_pData)
        {
            delete[] _pData;
            _pData = NULL;
        }
    }
    template <class T>
    friend ostream& operator<<(ostream& _cout, SymmetricMatrix &s)
    {
        for(size_t i=0; ifor(size_t j=0; j" ";
            _cout<return _cout;
    }
private:
    T* _pData;
    size_t _row;
    size_t _col;
};
int main()
{
    int arr[5][5] = {{0, 1, 2, 3, 4},
                     {1, 0, 1, 2, 3},
                     {2, 1, 0, 1, 2},
                     {3, 2, 1, 0, 1},
                     {4, 3, 2, 1, 0}};
    SymmetricMatrix<int> sm((int *)arr, sizeof(arr)/sizeof(arr[0]));
    cout<"pause");
    return 0;
}