C ++中多维数组的动态内存分配 [英] Dynamic Memory Allocation in C ++ for Multi Dimentional Array

问题描述

大家好

我正在寻找二维数组中的动态内存分配.在C ++中
我真正需要的是我需要"N"个数组数，其中我仅在运行时会得到"N"的值.

每个数组的大小都为"Z"，其中Z对于不同的数组将是不同的.

我想到了将二维数组用于同一数组，以便将所有射线组合成一个数组，但是问题是每个数组中的元素数都不相同.

例子是:

假设在运行时用户给出我需要输入4种类型的数据，所以在这里，N = 4


第一组有10个物品，所以这里z = 10
第二个有23个项目，所以这里z = 23
3rd有12个商品，所以这里z = 12
第四有90件.所以这里z = 90


这就是我需要的

任何指针！
如果我可以在C ++中使用相同的代码，那将是一个很大的帮助.

在此先感谢

Hi all

I am looking for Dynamic memory allocation in 2-D array. in C++
What exactly i Require is that I need ''N '' Number of Arrays, where in I would get value of ''N'' at runtime only.

Each Array would be of size say '' Z '', wherein Z would be differnt for different array.

I thought of having 2-D array for the same, so that I can have all arays combined in one, But then the problem is that number of element is different in each array.

example is :

Suppose at Runtime user gives that i need to enter 4 types of data, so here, N=4

The
1st set has 10 items, so here z=10
2nd has 23 items, so here z=23
3rd has 12 items, so here z=12
4th has 90 items. so here z=90


This is what i require

Any pointer !!!
It would be a great help if i can have a code in C++ for the same.

Thanks in Advance

推荐答案

您可以为此使用向量矢量.
假设您要存储的内容是int，那么您将创建一个矢量--

You can use a vector of vectors for this.
Suppose the contents you want to store are ints then you would create such a vector as -

std::vector<std::vector<int>> vvInt;

要分配第一组10个值，您可以执行以下操作-

To assign the first set of 10 values you could do this -

std::vector<int> vInt;

for (int i = 0; i < 10; ++i)
{
    vInt.push_back(i);
}

现在，将第一个集合添加到向量的向量中.

Now add this first set to the vector of vectors.

vvInt.push_back(vInt);

同样-

Similarly -

vInt.clear();

for (int i = 0; i < 23; ++i)
{
    vInt.push_back(i);
}

vvInt.push_back(vInt);

感谢您的解决方案.

甚至对我也有用

cout<< 输入要测试的套数"；
cin>> size_x;

a = new int * [size_x];
/* a = new(size_x * sizeof(int *)); */

对于(i = 0; i< size_x; i ++)
{
cout<< 输入组的编号elemnets"；
cin>> size_y;

a [i] = new int [size_y +1];
/* a [i] = new(size_y * sizeof(int)); */

for(j = 1; j< = size_y; j ++)
{
a [i] [0] = size_y;

cout<< 输入元素"；
cin>> a [i] [j];
}
}

Thanks For the solution.

Even this worked for me

cout << " Enter the number of sets you want to test ";
cin >> size_x;

a= new int *[size_x];
/* a = new (size_x * sizeof(int *)); */

for (i = 0; i < size_x; i++)
{
cout << " Enter the number elemnets for group ";
cin >> size_y;

a[i]= new int [size_y +1];
/* a[i] = new (size_y * sizeof(int)); */

for (j = 1; j <= size_y; j++)
{
a[i][0]=size_y;

cout << " Enter the elements " ;
cin >> a[i][j] ;
}
}

在这里，您必须注意分配和释放内存.
如果未正确完成此操作，则将发生内存泄漏.

vector将在内部为您分配内存，以确保没有内存泄漏.

Here you have to take care of allocating and deallocating memory.
If this is not done properly you will have memory leaks.

A vector will internally take care of memory allocation for you guaranteeing no memory leaks.

这篇关于C ++中多维数组的动态内存分配的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！