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Join Date: Jun 2006
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Junior Poster
I was wondering how I could access my several countryAttachedXX arrays(in this post they start on line 85), without many if statements, determined by user input. I was thinking maybe an array of arrays, but had difficulty finding out how to do that on the web. Thanks,
-Matt
-Matt
cplusplus Syntax (Toggle Plain Text)
Last edited by Matt Tacular : Jun 12th, 2007 at 8:49 am.
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>I was thinking maybe an array of arrays
You were thinking correctly. Something like this perhaps?
The only problem here is that each sub-array has to have the same number of cells (5 in the previous code). So if you want a ragged array you either need to do some dynamic allocation (which I don't recommend just yet) or pad the shorter arrays with a sentinel value like -1.
You were thinking correctly. Something like this perhaps?
#include <iostream>
#include <ios>
#include <limits>
int main()
{
int a[][5] = {
{1,2,3,4,5},
{5,4,3,2,1},
};
int index;
std::cout<<"Enter 1 for ascending or 2 for descending: ";
while ( !( std::cin>> index ) || !( index == 1 || index == 2 ) ) {
std::cerr<<"Invalid input\n";
std::cin.clear();
std::cin.ignore( std::numeric_limits<std::streamsize>::max(), '\n' );
std::cout<<"Enter 1 for ascending or 2 for descending: ";
}
for ( int i = 0; i < 5; i++ )
std::cout<< a[index - 1][i] <<' ';
std::cout<<'\n';
} I'm a programmer. My attitude starts with arrogance, holds steady at condescension, and ends with hostility. Get used to it.
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Join Date: Mar 2007
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what about doing it with a struct? this way every array is independent from the other, so you can create an array of structs...
now, what i would find complicated is instructing the structs the size of the array of ints... maybe creating an int variable in the struct that indicates the size of the array...
now, what i would find complicated is instructing the structs the size of the array of ints... maybe creating an int variable in the struct that indicates the size of the array...
-->sometimes i wanna take my toaster in a bath<-- •
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Junior Poster
Is there a way I can do an actual array of arrays? Not a multidimensional one. That way I could have different sized arrays in it. Or how could I do a pointer to an array, then an array of those pointers?
Last edited by Matt Tacular : Jun 12th, 2007 at 9:44 am.
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>Is there a way I can do an actual array of arrays? Not a multidimensional one.
There's no such thing as a multidimensional array in C++. It's always an array of arrays. What you want is a ragged array, and the only way to do it is to manually simulate the arrays:
That's a lot harder and a lot easier to screw up. Alternatively, and this is your best option, use a vector of vectors:
There's no such thing as a multidimensional array in C++. It's always an array of arrays. What you want is a ragged array, and the only way to do it is to manually simulate the arrays:
#include <iostream>
#include <ios>
#include <limits>
int main()
{
int **a = new int*[2];
a[0] = new int[5];
a[1] = new int[3];
for ( int i = 0; i < 5; i++ )
a[0][i] = i + 1;
for ( int i = 0; i < 3; i++ )
a[1][i] = 3 - i;
int index;
std::cout<<"Enter 1 for ascending or 2 for descending: ";
while ( !( std::cin>> index ) || !( index == 1 || index == 2 ) ) {
std::cerr<<"Invalid input\n";
std::cin.clear();
std::cin.ignore( std::numeric_limits<std::streamsize>::max(), '\n' );
std::cout<<"Enter 1 for ascending or 2 for descending: ";
}
int limit = 5;
if ( index != 1 )
limit = 3;
for ( int i = 0; i < limit; i++ )
std::cout<< a[index - 1][i] <<' ';
std::cout<<'\n';
delete[] a[1];
delete[] a[0];
delete[] a;
}#include <iostream>
#include <ios>
#include <limits>
#include <vector>
int main()
{
std::vector< std::vector<int> > v;
v.push_back ( std::vector<int> ( 5 ) );
v.push_back ( std::vector<int> ( 3 ) );
for ( int i = 0; i < 5; i++ )
v[0][i] = i + 1;
for ( int i = 0; i < 3; i++ )
v[1][i] = 3 - i;
std::vector<int>::size_type index;
std::cout<<"Enter 1 for ascending or 2 for descending: ";
while ( !( std::cin>> index ) || !( index == 1 || index == 2 ) ) {
std::cerr<<"Invalid input\n";
std::cin.clear();
std::cin.ignore( std::numeric_limits<std::streamsize>::max(), '\n' );
std::cout<<"Enter 1 for ascending or 2 for descending: ";
}
for ( std::vector<int>::size_type i = 0; i < v[index - 1].size(); i++ )
std::cout<< v[index - 1][i] <<' ';
std::cout<<'\n';
} I'm a programmer. My attitude starts with arrogance, holds steady at condescension, and ends with hostility. Get used to it.
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the problem is that in arrays of arrays all arrays have the same length, meaning the same quantity of elements, in this case, ints...
that's why i proposed the idea of using a struct with an int and an array of ints, where the int specifies the length of the array...
that's why i proposed the idea of using a struct with an int and an array of ints, where the int specifies the length of the array...
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>that's why i proposed the idea of using a struct with an int and an array
>of ints, where the int specifies the length of the array...
And that's different from a ragged array, how? You still have to dynamically allocate the memory for each instance of the structure. The only real benefit to an array of structures is you can easily store the size of each array. And of course, it's still inferior to using a vector of vectors.
>of ints, where the int specifies the length of the array...
And that's different from a ragged array, how? You still have to dynamically allocate the memory for each instance of the structure. The only real benefit to an array of structures is you can easily store the size of each array. And of course, it's still inferior to using a vector of vectors.
I'm a programmer. My attitude starts with arrogance, holds steady at condescension, and ends with hostility. Get used to it.
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