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Sep 30th, 2009

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Multimap

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Hi..
Suppose I have a multimap like below

C++ Syntax (Toggle Plain Text)
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));
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,

C++ Syntax (Toggle Plain Text)
  a 1 start
  a 5 end
  b 3 start
  b 4 middle
  b 6 end
  c 20 single
  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

C++ Syntax (Toggle Plain Text)
  m.insert(pair<string, int>("a", (int1,int2,string1,string2)));
  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

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Web_Sailor

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Oct 1st, 2009

-1

Re: Multimap

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

cpp Syntax (Toggle Plain Text)
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;
	}
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

Laiq Ahmed

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Oct 1st, 2009

Re: Multimap

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:-

C++ Syntax (Toggle Plain Text)
m.insert(pair<string, int>("a", (int1,int2,string1,string2)));
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

Last edited by Web_Sailor; Oct 1st, 2009 at 5:29 am.

Web_Sailor

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Oct 1st, 2009

Re: Multimap

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

Why not create your own object/class?

C++ Syntax (Toggle Plain Text)
 
class Something
{
public:
     char letter;  //a
     int length;   //3
     string pos;  //start
}
class Something
{
public:
     char letter;  //a
     int length;   //3
     string pos;  //start
}

And then store this in a vector?

Last edited by iamthwee; Oct 1st, 2009 at 5:50 am.

iamthwee

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Oct 1st, 2009

Re: Multimap

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

Web_Sailor

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Oct 2nd, 2009

Re: Multimap

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:

(Toggle Plain Text)

  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.

(Toggle Plain Text)

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

Last edited by iamthwee; Oct 2nd, 2009 at 5:34 am.

iamthwee

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Oct 2nd, 2009

Re: Multimap

For example....

C++ Syntax (Toggle Plain Text)
#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;
}
#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;
}

iamthwee

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Oct 4th, 2009

Re: Multimap

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

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