C ++ 2维数组大小可变的行 [英] C++ 2 dimensional array with variable size rows

问题描述

您如何创建一个二维数组，比方说，改编[] [] 5行，每行中有一个可变的列数？

How can you create a 2D array,say, arr[][] with 5 rows and each row has a variable number of columns in it?

可能改编[5] []
与第一行改编[0] [] 4个列

第二行改编[1] [] 5列等等？

我不介意一个STL向量解决方案，但我不知道向量很好呢。

I wouldn't mind a STL vector solution but I don't know vectors very well yet.

推荐答案

使用C ++ 11，可以方便地与向量做（行breakes增加了可读性）：

With C++11, you can do it easily with vectors (line breakes added for readability):

std::vector< std::vector <int > > arr = {
{1,2,3},
{4,5},
{6,7,8,9,0}
};

如果你没有一个C ++编译器11，它的工作方式不尽相同，但你不能对他们进行初始化一样简单。您可以单独设置元素：

If you don't have a C++11 compiler, it works the exact same way, but you will not be able to initialize them as easy. You can set elements individually:

std::vector< std::vector <int > > arr;//vector of vectors. Think of each element as of a "row"
std::vector<int> sub;//a temporary "row"
sub.push_back(1);
sub.push_back(2);
arr.push_back(sub);//Adding a "row" to the vector
sub.clear();//Making another one
sub.push_back(1);
sub.push_back(12);
sub.push_back(54);
arr.push_back(sub);//Adding another "row" to the vector

或者，您可以初始化每个行在普通的数组：

Or you can initialize each "row" with an ordinary array:

std::vector< std::vector <int > > arr;
static const int arr[] = {1,2,3,4};//A "row" as an ordinary array
vector<int> vec (arr, arr + sizeof(arr) / sizeof(arr[0]) ); //Setting a "Row" as a vector
arr.push_back(vec);//Adding the "row" to the vector of vectors. 

这不完全可以做你想做的与普通阵列，因为当你做一个数组[X] [Y] ，它automaticaly是 X * Y 矩阵。你可以，但是，使用指针数组：

It's not exactly possible to do what you want with ordinary arrays, since when you make an array[X][Y], it automaticaly is an X*Y matrix. You could, however, use an array of pointers:

int * array[3];
//also possible: int ** array =  new int*[3]; but don't forget to delete it afterwards.
int sub1[3] = {1,2,3};
int sub2[2] = {1,2};
int sub3[4] = {1,2,3,4};
array[0] = sub1;
array[1] = sub2;
array[2] = sub3;

和数组[X]访问的元素[Y] 。但是，向量的解决方案是更好的整体。

and access elements with array[X][Y]. However, the vector solution is much better overall.

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