C++ 向量向量的初始化？
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Initialization of a vector of vectors?
提问by Eric
Is there a way to initialize a vector of vectors in the same ,quick, manner as you initialize a matrix?
有没有办法以与初始化矩阵相同的快速方式来初始化向量向量？
typedef int type;
type matrix[2][2]=
{
{1,0},{0,1}
};
vector<vector<type> > vectorMatrix; //???
采纳答案by sinek
For the single vector you can use following:
对于单个向量，您可以使用以下内容：
typedef int type;
type elements[] = {0,1,2,3,4,5,6,7,8,9};
vector<int> vec(elements, elements + sizeof(elements) / sizeof(type) );
Based on that you could use following:
基于此，您可以使用以下内容：
type matrix[2][2]=
{
{1,0},{0,1}
};
vector<int> row_0_vec(matrix[0], matrix[0] + sizeof(matrix[0]) / sizeof(type) );
vector<int> row_1_vec(matrix[1], matrix[1] + sizeof(matrix[1]) / sizeof(type) );
vector<vector<type> > vectorMatrix;
vectorMatrix.push_back(row_0_vec);
vectorMatrix.push_back(row_1_vec);
In c++0x, you be able to initialize standard containers in a same way as arrays.
在c++0x 中，您可以以与数组相同的方式初始化标准容器。
回答by Brett
std::vector<std::vector<int>> vector_of_vectors;
then if you want to add, you can use this procedure:
那么如果你想添加，你可以使用这个程序：
vector_of_vectors.resize(#rows); //just changed the number of rows in the vector
vector_of_vectors[row#].push_back(someInt); //this adds a column
Or you can do something like this:
或者你可以做这样的事情：
std::vector<int> myRow;
myRow.push_back(someInt);
vector_of_vectors.push_back(myRow);
So, in your case, you should be able to say:
所以，在你的情况下，你应该能够说：
vector_of_vectors.resize(2);
vector_of_vectors[0].resize(2);
vector_of_vectors[1].resize(2);
for(int i=0; i < 2; i++)
for(int j=0; j < 2; j++)
vector_of_vectors[i][j] = yourInt;
回答by Mike Seymour
In C++0x, I think you can use the same syntax as for your matrix.
在 C++0x 中，我认为您可以使用与matrix.
In C++03, you have to write some tedious code to populate it. Boost.Assign might be able to simplify it somewhat, using something like the following untested code:
在 C++03 中，您必须编写一些繁琐的代码来填充它。Boost.Assign 可能会稍微简化它，使用类似以下未经测试的代码：
#include <boost/assign/std/vector.hpp>
vector<vector<type> > v;
v += list_of(1)(0), list_of(0)(1);
or even
甚至
vector<vector<type> > v = list_of(list_of(1)(0))(list_of(0)(1));
回答by Umang
If the matrix is completely filled -
如果矩阵完全填充 -
vector< vector<int> > TwoDVec(ROWS, vector<int>(COLS));
//Returns a matrix of dimensions ROWS*COLS with all elements as 0
//Initialize as -
TwoDVec[0][0] = 0;
TwoDVec[0][1] = 1;
..
.
Update : I found there's a better way here
更新：我发现有一个更好的办法在这里
else if there are variable number of elements in each row(not a matrix) -
否则如果每行中有可变数量的元素（不是矩阵） -
vector< vector<int> > TwoDVec(ROWS);
for(int i=0; i<ROWS; i++){
while(there_are_elements_in_row[i]){ //pseudocode
TwoDVec[i].push_back(element);
}
}
