C++ 由另一个数组中的值组成的数组
如果我有一个如下所示的数组:C++ 由另一个数组中的值组成的数组,c++,arrays,multidimensional-array,C++,Arrays,Multidimensional Array,如果我有一个如下所示的数组: int map[21][28] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
int map[21][28] =
{
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 2, 2, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};
int zoomedMap[7][7] =
{
2, 2, 1, 1, 1, 1, 1,
1, 0, 0, 0, 0, 0, 1,
1, 0, 0, 0, 0, 0, 1,
1, 0, 0, 0, 0, 0, 1,
1, 0, 0, 0, 0, 0, 1,
1, 0, 0, 0, 0, 0, 1,
1, 1, 1, 1, 1, 1, 1
};
如何创建由该数组中的值组成的较小数组?有点像这样:
int map[21][28] =
{
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 2, 2, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};
int zoomedMap[7][7] =
{
2, 2, 1, 1, 1, 1, 1,
1, 0, 0, 0, 0, 0, 1,
1, 0, 0, 0, 0, 0, 1,
1, 0, 0, 0, 0, 0, 1,
1, 0, 0, 0, 0, 0, 1,
1, 0, 0, 0, 0, 0, 1,
1, 1, 1, 1, 1, 1, 1
};
我不知道这是否有帮助,但是:
- 我知道两个阵列的确切尺寸
- 我希望能够移动较小的数组位置,最好只更改X/Y值
本质上,zoomedMap应该只是一个指向更大矩阵的智能指针,它了解如何取消引用并获得正确的结果。您始终可以通过循环静态执行:
const int pos_x = 6, pos_y = 7, size_x = 7, size_y = 7;
int newMap[size_x][size_y] = {0};
for( int i = pos_x; i != pos_x+size_x; ++i ) {
for( int j = pos_y; j != pos_y+size_y; ++j) {
newMap[i-pos_x][j-pos_y] = map[i][j];
}
}
虽然这不是很安全,而且很难动态工作。
您可能想编写一个包含所需函数的矩阵包装器类;或者找到一个已经存在并扩展它(我将开始研究STL或Boost以获得一个现有的矩阵类)很明显,您的子数组实际上只是主数组中的一个“数据块”(带有一些有趣的分区)。假设您正在检查边界,并且不允许发生越界情况,则可以使用指针数学和有关主数组的一些基本信息来模拟子数组
- 块将始终是距离
位置的一些[0][0]
偏移量,因此我们需要这些值(row和column)[row][column]
- 块具有固定的宽度,因此
不会超过主数组宽度。我们需要那个宽度列+宽度
- 块具有固定的高度,因此
不会超过主阵列高度。我们需要那个高度行+高度
- 我希望很明显,我们需要作为主数组的基址(在您的例子中是
)map
// internal rerefential to a submatrix in a larger fixed matrix.
template<typename T>
class Sub2D
{
public:
template<size_t R, size_t C>
Sub2D(T(&ar)[R][C], int top, int left, int height, int width)
: parent(ar[0])
, row(top)
, col(left)
, max_row(R)
, max_col(C)
{
if ((row+width) >= R || (col+height) >= C)
throw std::out_of_range("");
}
// retrieve our subrow offset into the main 2D array
T* operator [](size_t n)
{
// enable at your desire, but as Alex pointed out, all
// the standard containers let you shoot yourself in the
// foot with this operator. why not this one too =P
//if (row+n >= max_row)
// throw std::out_of_range("");
return parent + ((row+n)*max_col + col);
}
private:
T* parent;
size_t row, col;
size_t max_row, max_col;
};
请注意,9现在位于我们期望的位置
显然,您可以向这样一个模板类添加更多内容,包括更好的范围检查、移动指针、将快照插入其他内存缓冲区等,但重点是基本的给我这个子矩阵一个指针和一些偏移量是很难击败的,尤其是在性能方面。根据您的要求,这可能足以:
int (*zoomedMap)[28] = reinterpret_cast<int (*)[28]>(&map[X][Y]);
int(*zoomedMap)[28]=重新解释投射(&map[X][Y]);
这将为您提供一个标识符,您可以像使用二维数组一样使用它:zoomedMap[i][j]
。通过为放大的地图分配新地址,可以轻松地在较大的数组中移动该地图
这取决于C++实现,允许一个指针浮动到一个浮点数组的指针,只要所有引用保持在原始数组中。这是常见的
它使
zoomedMap
指向与map
相同的内存。因此,如果不更改另一个,则无法更改其中一个。如果您想这样做,您需要制作一个副本。如果您想让它高效且具有参考性,您不需要数组;你需要一个指针,一个(X,Y)坐标元组,一个宽度+高度元组,还有一些数学。我不知道怎么做。你能用一些伪代码或实际代码发布一个答案吗?当然可以。它很简单,就像C/C++中的常规数组一样,它不会阻止你自我解嘲,但它至少会给你一个或两个想法。那么,你对矩阵的列主序或行主序有了深入的了解吗?您理解在矩阵运算中使用C++指针的限制吗?看起来不错,但我认为操作符[]不应该抛出异常,将其留给AT-()。操作员[]应该是不安全的,但效率很高。@AlexChamberlain关于[]的观点很好。很快更新。就像我说的。真是厌食症的表现。