Dynamic Memory Allocation in C ++ for Multi Dimentional Array

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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

Posted 13-Feb-10 11:56am

ashishqwerty

Updated 13-Feb-10 12:06pm

v2

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3 solutions

Solution 2

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] ;
}
}

Posted 13-Feb-10 17:30pm

ashishqwerty

Updated 13-Feb-10 17:42pm

v3

Solution 3

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.

Posted 13-Feb-10 17:39pm

«_Superman_»

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«_Superman_» · Accepted Answer · 2010-02-13T16:46:00

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;

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);
}

Now add this first set to the vector of vectors.

vvInt.push_back(vInt);

Similarly -

vInt.clear();

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

vvInt.push_back(vInt);