如何将二维向量传递给 C++ 中的函数？
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How to pass 2-D vector to a function in C++?
提问by bsoundra
If it is passed, is it passed by value or by reference?
如果传递，是按值传递还是按引用传递？
void printMatrix(vector<vector<int>> *matrix);
...
vector<vector<int>> matrix(3, vector<int>(3,0));
printMatrix(&matrix1);
回答by casablanca
Since your function declaration:
由于您的函数声明：
void printMatrix(vector< vector<int> > *matrix)
specifies a pointer, it is essentially passed by reference. However, in C++, it's better to avoid pointers and pass a reference directly:
指定一个指针，它本质上是通过引用传递的。但是，在 C++ 中，最好避免使用指针并直接传递引用：
void printMatrix(vector< vector<int> > &matrix)
and
和
printMatrix(matrix1); // Function call
This looks like a normal function call, but it is passed by reference as indicated in the function declaration. This saves you from unnecessary pointer dereferences.
这看起来像一个普通的函数调用，但它是通过引用传递的，如函数声明中所示。这可以避免不必要的指针取消引用。
回答by Pablo Ruiz Ruiz
Why not passing just the 2d vector?
为什么不只传递二维向量？
void printMatrix(vector < vector<int> > matrix)
{
cout << "[";
for(int i=0; i<matrix.size(); i++)
{
cout << "[" << matrix[i][0];
for(int j=0; j<matrix[0].size(); j++)
{
cout << ", " << matrix[i][j];
}
cout << "]" << endl;
}
cout << "]" << endl;
}
vector < vector<int> > twoDvector;
vector<int> row(3,2);
for(int i=0; i<5; i++)
{
twoDvector.push_back(row);
}
printMatrix(twoDvector);
回答by Benjamin Lindley
Well, first of all, you're creating it wrong.
嗯，首先，你创建它是错误的。
vector<vector<int>> matrix1(3, vector<int>(3,0));
You can pass by value or by reference, or by pointer(not recommended). If you're passing to a function that doesn't change the contents, you can either pass by value, or by const reference. I would prefer const reference, some people think the "correct" way is to pass by value.
您可以按值或按引用或按指针传递（不推荐）。如果要传递给不更改内容的函数，则可以按值传递，也可以按常量引用传递。我更喜欢 const 引用，有些人认为“正确”的方法是按值传递。
void printMatrix(const vector<vector<int>> & matrix);
// or
void printMatrix(vector<vector<int>> matrix);
// to call
printMatrix(matrix1);
