Thread: Set question

Let me model my requirement with a simple example...

I use multiset as a part of my program...
say for eg: 500,400,300,200,100
are the value to be inserted in the set

All i have to do is assoaciate each elemnt above with some specified number..

say 500 assoaciated with 1
sameways:
400-2
300-3
200-4
100-5

whenevere the elemnts are pushed and finally extracted(ofcourse minelement is extrcted if minheap)

say 100 is extracted...Now i should be ina postion to get its associated index ie '5' straight away...

how do i map them...???
plz help me to get it solved

How do you map them? Why not use a (multi)map?

can u plz elabrate on it...plz
should i use map with set
wats the syntax... how does it meet my requirement

Originally Posted by dpp

can u plz elabrate on it...plz
should i use map with set
wats the syntax... how does it meet my requirement

A map is your requirement -- a bunch of pairs of values, each a data value associated with a key value, stored in sorted order by keys.

Whatever resource you learned sets from, flip forward three pages or so and you'll find map.

but will map be in sorted order

Plz let me know is there a function for sort in map....

It is not contiguous as far as i know

As I mentioned before, elements in a map are stored in sorted order by keys. (You can specify your own ordering function if you want.)

If you have lost your book between hearing about sets and trying to do this now, you can always find things on the web.

erasing doubt ;(

Code:

 mymap.insert ( pair<long long int ,long long int>(200,1) );
           mymap.insert ( pair<long long int ,long long int>(201,2) );
            mymap.insert ( pair<long long int ,long long int>(201,3) );
            it=mymap.find(1);
               mymap.erase (it);

all i wanted is to erase the elemnt with the mapped value 1...
but this doesnt work

but i am able to do mympa.erase(201) (delete by key which i dont need)


I want it to erase based on the mappd value

1) What if there's more than one element with that value?
2) What if there's no element with that value?
3) To find an element with a given value, you need to use find_if.

(I suppose I should add that find_if is not a member of multimap, but a generic <algorithm>.)

But for the example i mentioned above

1 was an element
but still it dint work

why???

when i did

Code:

it=mymap.find(1);
               mymap.erase (it);

this, The corresponding elemnt was not erased....
Though '1' is a part of the elements

Originally Posted by dpp

But for the example i mentioned above

1 was an element
but still it dint work

why???

1 is most definitely not an element. 200 is, and 201, and another 201. Read the last answer again.

oops sorry...

if i do

Code:

mymap1.erase(201)

if 201 has more than one elements being mapped (but i want only one of its mapped value to be removed)
Is it possible to do that

Code:

mymap.insert ( pair<long long int ,long long int>(200,1) );
           mymap.insert ( pair<long long int ,long long int>(201,2) );
            mymap.insert ( pair<long long int ,long long int>(201,3) );

say i want only 201,2 to be removed but not 201,3...

Thanks for ur patience

i found it thanks