[英]Initializing multidimensional array C++
In C++, when I want to initialize an array of some length (of integers for instance) I can just write 在C ++中,当我想初始化一些长度(例如整数)的数组时,我可以写
int* tab;
tab = new int[size];
where size is given somewhere else. 在其他地方给出尺寸的地方。 But how do I do that in the same manner, when it comes to a multidimensional array?
但是当涉及多维数组时,我该如何以相同的方式做到这一点? I can't just add another dimension(s) in the second line, because compiler doesn't like that...
我不能在第二行添加另一个维度,因为编译器不喜欢这样...
It's a simple question I guess. 我想这是一个简单的问题。 I need that, as I'm writing an assignment in object-oriented programming and 2D array is a private part of a class, which needs to be... constructed in the constructor (with 2 dimensions as parameters).
我需要这样,因为我在面向对象编程中编写了一个赋值,而2D数组是一个类的私有部分,它需要在构造函数中构造(以2维作为参数)。
Using std::vector
is the safe way: 使用
std::vector
是安全的方法:
std::vector<std::vector<int>> mat(size1, std::vector<int>(size2));
if really you want to use new
yourself: 如果真的想要自己使用
new
:
int** mat = new int*[size1];
for (std::size_t i = 0; i != size1; ++i) {
mat[i] = new int[size2];
}
And don't forget to clean resources: 不要忘记清理资源:
for (std::size_t i = 0; i != size1; ++i) {
delete [] mat[i];
}
delete[] mat;
If you can afford std::vector
instead of arrays you can use as syntax: 如果你能买得起
std::vector
而不是数组你可以用作语法:
std::vector< std::vector<int> > matrix(rows, std::vector<int>(columns));
for (int i=0; i<rows; i++) {
for (int j=0; j<columns; j++) {
matrix[i][j] = i+j;
}
}
If you get height/width parameters before the initialization of the array you can try: 如果在初始化数组之前获得高度/宽度参数,可以尝试:
int height = 10;
int width = 10;
//...
int tab[heigth][width];
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