在 C++ 中声明可变长度二维数组的正确方法
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/8294102/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Proper way to declare a variable length two dimensional array in C++
提问by Christian
I would like to get a two dimensional int array arrthat I can access via arr[i][j].
我想获得一个arr可以通过 arr[i][j] 访问的二维 int 数组。
As far as I understand I could declare int arr[10][15];to get such an array.
In my case the size is however variable and as far as I understand this syntax doesn't work if the size of the array isn't hardcoded but I use a variable like int arr[sizeX][sizeY].
据我所知，我可以声明int arr[10][15];获得这样的数组。在我的情况下，大小是可变的，据我所知，如果数组的大小不是硬编码的，则此语法不起作用，但我使用像int arr[sizeX][sizeY].
What's the best workaround?
最好的解决方法是什么？
回答by Some programmer dude
If you don't want to use a std::vectorof vectors (or the new C++11 std::array) then you have to allocate all sub-arrays manually:
如果您不想使用 a std::vectorof 向量（或新的 C++11 std::array），则必须手动分配所有子数组：
int **arr = new int* [sizeX];
for (int i = 0; i < sizeX; i++)
arr[i] = new int[sizeY];
And of course don't forget to delete[]all when done.
当然，完成后不要忘记delete[]所有人。
回答by BruceAdi
c/c++ does not support multidimensional array. But it does support array of array:
c/c++ 不支持多维数组。但它确实支持数组数组：
//simulate 2-dimension array with 1-dimension array
{
int x = 20;
int y = 40;
int * ar = new int(x*y);
int idx_x =9;
int idx_y=12;
ar[idx_x + idx_y * x] = 23;
}
//simulate 2-dimension array with array of array
{
int x = 20;
int y = 40;
int**ar = new int*[y];
for(int i = 0; i< y; ++i)
{
ar[i] = new int[x];
}
ar[9][12] = 0;
}
回答by cpp
As fefe said you can use vector of vectors, e. g. :
正如fefe所说，您可以使用向量向量，例如：
#include<iostream>
#include<vector>
using namespace std;
int main()
{
vector< vector<int> > vec;
vector<int> row1;
row1.push_back(1);
row1.push_back(2);
vector<int> row2;
row2.push_back(3);
row2.push_back(4);
vec.push_back(row1);
vec.push_back(row2);
for( int ix = 0; ix < 2; ++ix)
for( int jx = 0; jx < 2; ++jx)
cout << "[" << ix << ", " << jx << "] = " << vec[ix][jx] << endl;
}
回答by Chris Parton
If you're looking for the solution in C, see this Stack Overflow thread: How do I work with dynamic multi-dimensional arrays in C?.
如果您正在寻找 C 中的解决方案，请参阅此堆栈溢出线程： 如何在 C 中使用动态多维数组？.
If C++ is okay, then you can create a 2D vector, i.e. a vector of vectors. See http://www.cplusplus.com/forum/general/833/.
如果C++没问题，那么你可以创建一个二维向量，即向量的向量。请参阅http://www.cplusplus.com/forum/general/833/。
回答by Daniel Daranas
You can't, with array syntax. The language requires that you use compile time constants to create arrays.
你不能，用数组语法。该语言要求您使用编译时常量来创建数组。
回答by fefe
C++ does not have variable length arrays. You can consider using vector<vector<int> >. It can be also accessed using arr[i][j].
C++ 没有变长数组。您可以考虑使用vector<vector<int> >. 也可以使用arr[i][j].
