C++ 多维向量初始化
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/6491251/
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
Multi-dimensional vector initialization
提问by Avinash
I have following std::vectordeclaration:
我有以下std::vector声明：
std::vector<std::vector<std::vector<int> > > m_input;
std::vector<std::vector<std::vector<int> > > m_input;
I am initializing it as follows:
我将其初始化如下：
m_input.resize (100);
m_output.resize(100);
for (int i = 0; i < 100; ++i) {
m_input [i].resize(100);
m_output[i].resize(100);
for (int j = 0; j < 100; ++j){
m_input [i][j].resize(100);
m_output[i][j].resize(100);
}
}
How can I achieve this via the member initializer list?
如何通过成员初始值设定项列表实现此目的？
回答by MSalters
std::vector<T>has a constructor that takes two arguments, a number of elements and an initial value. In your case, you want to initialize m_inputwith 100 copies of a std::vector<std::vector<int> >, so it'd be : m_input(100, X). Now, that Xin turn is a vector of 100 std::vector<int>, which in turn contains a hundred ints:
std::vector<T>有一个构造函数，它接受两个参数，一个元素数量和一个初始值。在您的情况下，您希望m_input使用 100 个副本进行初始化std::vector<std::vector<int> >，因此它是: m_input(100, X). 现在，这X又是一个 100 的向量，std::vector<int>它又包含一百个整数：
: m_input(100, std::vector<std::vector<int> >(100, std::vector<int>(100, 0)))
: m_input(100, std::vector<std::vector<int> >(100, std::vector<int>(100, 0)))
回答by sbi
my_class::my_class()
: m_input(100, std::vector< std::vector<int> >(100, std::vector<int>(100) ))
{
}
That said, implementing a multi-dimensional field should be done by projecting into a one-dimensional one, as Viktor said in his comment to the question.
也就是说，正如 Viktor 在对该问题的评论中所说的那样，应该通过投影到一维领域来实现多维领域。
回答by deceleratedcaviar
If you can assert that your vector dimensions are going to be of a fixed length, then why not use std::array?
如果您可以断言您的向量维度将具有固定长度，那么为什么不使用std::array？
For example:
例如：
std:array<std::array<std::array<int, 100>, 100>, 100>
std:array<std::array<std::array<int, 100>, 100>, 100>
That way you can take advantage of all the memory being contiguously allocated (as hinted at by Viktor_Sehrin the comments), without the added implementation woes of accessing a 1-dimensional array in a 3-dimensional way.
这样您就可以利用所有连续分配的内存（如Viktor_Sehr在评论中暗示的 那样），而不会增加以 3 维方式访问 1 维数组的实现问题。
