Multimap

[Web_Sailor]

Hi..
Suppose I have a multimap like below

multimap<string, int> m;

  m.insert(pair<string, int>("a", 1));
  m.insert(pair<string, int>("c", 20));
  m.insert(pair<string, int>("b", 3));
  m.insert(pair<string, int>("b", 4));
  m.insert(pair<string, int>("a", 5));
  m.insert(pair<string, int>("b", 6));

I want to print a output flags for first element, middle element and last element for multi map. Like e.g,

a 1 start
  a 5 end
  b 3 start
  b 4 middle
  b 6 end
  c 20 single

Also suppose I want to get the maximum length in a a field. Like here I should get maximum length = 2 which is for c.
Then if suppose I want to format it and set the fix length for this field as 2.

Also lets suppose I want the value to have more than one value like

m.insert(pair<string, int>("a", (int1,int2,string1,string2)));

That means for my key a I have got more than 2 values. How can I make it work since pair is not working in this case ?

Thanks :)

[Laiq Ahmed]

Hi,
your question is bit unclear... what are you storing in the multimap logically. What I've understood is that you want to get the multiple values against the same key

multimap<int, string>  mm;
	mm.insert(std::make_pair(1, "a"));
	mm.insert(std::make_pair(1, "c"));
	mm.insert(std::make_pair(2, "d"));
	mm.insert(std::make_pair(2, "e"));

	typedef pair<multimap<int, string>::iterator, multimap<int, string>::iterator>  Pair_Range;
	Pair_Range  pRange = mm.equal_range(1);
	
	for (multimap<int, string>::iterator it = pRange.first; it != pRange.second; ++it) {
		cout << it->second<<endl;
	}

Hope this helps

[Web_Sailor]

I think I was clear in my question.

Well I solved the last part where I was showing something like this since I have no experience in using map:-

m.insert(pair<string, int>("a", (int1,int2,string1,string2)));

I simply added the required string arrays like this :-

strcombo = str1 +"\t"+ str2 +"\t"+ str3

and then created map like this ;-

multimap<string , string> mmmap;

and then :-

mmmap.insert(pair<string, string>(strcombo, str1));

So it solved my problem.

Now the first problem is still there:-

1) I want to print the flags for the first / middle and the last value for each key ?

Hope I can get some advice on that.

Thanks :)

[iamthwee]

Hmm, I don't know why you're fixated on using a map.

Why not create your own object/class?

class Something
{
public:
     char letter;  //a
     int length;   //3
     string pos;  //start
}

And then store this in a vector?

[Web_Sailor]

Yes I think Multimap will not be able to do such an operation. I had discussion with lot of people about it. So the best way would be to use a Vector I guess inside a beautiful class :)

Thanks

[iamthwee]

Yep, and thinking out aloud...

I assume you have to add the third parameter pos which will either be single, start-end or start-middle-end and no other case.

Therefore if you sort your file by letter so that

you have:

a 1 start
  a 5 end
  
  b 3 start
  b 4 middle
  b 6 end
  
  c 20 single

Your algo would to count the number of entries per letter.

if count = 1 then
 single
else if count = 2 then
 start end
else if count = 3 then
 start middle end
else
 discard (bad data)

And the following snippet might be useful when you come to custom sort your class...

http://www.daniweb.com/code/snippet217098.html

[iamthwee]

For example....

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

using namespace std;

class Foo
{
public:
   string name;
   double length;
};

//This functions sort by name THEN length
bool SortFooByNameThenLength ( const Foo& left, const Foo& right )
{

   if ( left.name > right.name )
   {
      return false;
   }
   else if ( left.name < right.name )
   {
      return true;
   }
   
   /*if letters are both the same now go to length and sort by
     that instead
     */
   else 
   {  
      /*note the difference, left.LENGTH
        instead of left.NAME
        */
      if (left.length > right.length )
      {
        return false;
      }
      
      else 
      { 
        return true;
      }  
   }
}



int main()
{
    
   Foo test;
   vector <Foo> myFoo;

   test.name = "a";
   test.length = 1;

   myFoo.push_back(test);
   
  
   test.name = "b";
   test.length = 5;
   
   myFoo.push_back(test);

   test.name = "a";
   test.length = 5;
   
   myFoo.push_back(test);
   
   test.name = "b";
   test.length = 6;
   
   myFoo.push_back(test);
   
   test.name = "b";
   test.length = 3;
   
   myFoo.push_back(test);
   
   test.name = "c";
   test.length = 20;
   
   myFoo.push_back(test);
   



   // call the sort like this 
   std::sort(myFoo.begin(), myFoo.end(), SortFooByNameThenLength);
   
   
   for ( unsigned int i = 0; i < myFoo.size(); i++ )
   {
     cout <<myFoo[i].name << " " << myFoo[i].length << endl;
   }
   
   cin.get();
   return 0;
}

[Web_Sailor]

Great :) Thanks. I think it should be a good starter for me.

Appreciate your advice. I will work on it and get back if I get into some trouble.

Thanks