Even and odd items in a list C++

[looxztation]

Hi, I have this list with items. I want the items in the list 0,2,4,6 and so on depening on the number of items the user put in the list.

After selecting the even numbers do I want to randomize the even numbers in to a textbox in windows form. But the following item after the even one is connected to the first one.

i1 = glosa->Count; 
srand (time(NULL));
if(i1%2 != 0)
i1 += 1;
i1= rand()% glosa->Count;			 
i = i1;
tbx_SvarSv->AppendText(glosa[i]);

This code is printing all of the items in the list in a randome order. This is wrong.

Thanks.

[Chervil]

Instead of trying to relate an item to the adjacent item, if they must stay together, perhaps you should use some data structure to keep them together.
A struct or class would do.

struct group {
    string one;
    string two;
}

then instead of a list of strings, use a list of group objects.

Or use the std::pair
http://www.cplusplus.com/reference/utility/pair/

[looxztation]

How do I use the std::pair funtion in a list full of strings?

[Chervil]

You would replace the 'list full of strings' with a list full of pairs.
Each pair would contain two strings.

[looxztation]

I'm so greatful for your help! How would you write a code with list full of pairs. Never used the pair funtion before! BIG thanks!

[Chervil]

Just an example code to give you some ideas. Here I used a vector rather than a list to store the data. Only reason for that was so I could use the random_shuffle.

#include <iostream>
#include <string>
#include <utility>
#include <vector>
#include <sstream>
#include <algorithm>

std::istringstream fin (
"peach 1 "
"apple 2 "
"orange 3 "
"grape 4 "
"banana 5 "
);

int main()
{
    typedef  std::pair<std::string, std::string> item;     // for simplicity
    
    std::vector<item> items;                               // container 
    
    std::string one, two;
    
    while (fin >> one >> two)                              // get the input and store it
        items.push_back(make_pair(one, two));
        
    std::cout << "\n\n----- input -----\n\n";              // display what we have 
    for (auto &a : items)
        std::cout << a.first << " " << a.second << '\n';
    
    std::cout << "\n\n----- sort ------\n\n";              // sort and redisplay

    std::sort(items.begin(), items.end());
    
    for (auto &a : items)
        std::cout << a.first << " " << a.second << '\n';
    
    std::cout << "\n\n--- shuffle -----\n\n";              // shuffle and redisplay
        
    std::random_shuffle(items.begin(), items.end());
        
    for (auto &a : items)
        std::cout << a.first << " " << a.second << '\n';
    
}

Sample output:

----- input -----

peach 1
apple 2
orange 3
grape 4
banana 5


----- sort ------

apple 2
banana 5
grape 4
orange 3
peach 1


--- shuffle -----

peach 1
banana 5
orange 3
grape 4
apple 2

[looxztation]

Thats a great code for me to use! I'm currently having problem to use this with windows form. How do I modify it to be used with windows form?

[Chervil]

How do I modify it to be used with windows form?

First, you can re-write the loops I used if necessary

    for (auto &a : items)
        std::cout << a.first << " " << a.second << '\n';

    for (unsigned int i=0; i<items.size(); i++)
        std::cout << items[i].first << " " << items[i].second << '\n';

Either way, instead of printing the first and second,, you would I guess want to use something like

AppendText(a.first) 
AppendText(a.second) 

or

AppendText(items[i].first) 
AppendText(items[i].second)

or something like that.


You may need to ask someone else to help, if you can't figure it out yourself.

[looxztation]

I do not get the pair funtion to work in my project at all. There is a syntex error for:
pair <String^, String^> item;

Do you know why?

I will try to get someone, thanks.

[Chervil]

String^

here I am out of my depth as this isn't standard C++ at all, it's some sort of Microsoft proprietary language.

[looxztation]

I see, its called "Windows From Project". I'm having a hard time to translate orginal C++ code to the windows form format. Thanks anyways!

[Chervil]

If you do a google search for "std::string to String^" there are lots of links, some may be what you want.