C++ 如何初始化结构上的向量向量？
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How to initialize a vector of vectors on a struct?
提问by anat0lius
If I have a NxN matrix
如果我有一个 NxN 矩阵
vector< vector<int> > A;
How should I initialize it?
我应该如何初始化它？
I've tried with no success:
我试过没有成功：
A = new vector(dimension);
neither:
两者都不：
A = new vector(dimension,vector<int>(dimension));
回答by Joseph Mansfield
You use newto perform dynamic allocation. It returns a pointer that points to the dynamically allocated object.
您用于new执行动态分配。它返回一个指向动态分配对象的指针。
You have no reason to use new, since Ais an automatic variable. You can simply initialise Ausing its constructor:
您没有理由使用new，因为它A是一个自动变量。您可以简单地A使用其构造函数进行初始化：
vector<vector<int> > A(dimension, vector<int>(dimension));
回答by Kerrek SB
Like this:
像这样：
#include <vector>
// ...
std::vector<std::vector<int>> A(dimension, std::vector<int>(dimension));
(Pre-C++11 you need to leave whitespace between the angled brackets.)
（在 C++11 之前，您需要在尖括号之间留出空格。）
