Removing from a vector of sets

[Snnnider]

Hello, I have a vector of sets in which I wish to remove a set from the vector, if it contains a certain value, is there any way of doing this?

for(int j = 0; j <= clauseVector.size(); ++j){
  if(clauseVector[j].find(find) != clauseVector[j].end())
    std::cout << "FOUND: " << propagator << "\n";
    }
  }

This is what I have been using to find the element, but is there a way to remove the set that contains the element?

If needed I can include the full code

Thank you

[Danny Toledo]

It almost sounds like you are looking for vector::erase: http://www.cplusplus.com/reference/vector/vector/erase/

[Snnnider]

Thats what I thought, but im getting segmentation faults

for(int j = 0; j <= clauseVector.size(); ++j){
  if(clauseVector[j].find(propagator) != clauseVector[j].end())
    clauseVector.erase (clauseVector.begin()+j);
 }

[Danny Toledo]

for(int j = 0; j <= clauseVector.size(); ++j)
The range for j should b 0 to size - 1, you currently have it as 0 to size.

[ne555]

clauseVector[ clauseVector.size() ] is out of bounds.
Also, if you `erase()' an element you shouldn't increment the index (¿do you realize why?)

[Snnnider]

@Danny Toledo, I have corrected this but am still getting segmentation faults

@ne555, In what way do you mean?

Once I have removed all instances of (find), it will be updated to a new int in order to remove those as well

Thank you both for your time

[JLBorges]

Something like this (example assumes that propagator is a string):

auto iter = std::find_if( clauseVector.begin(), clauseVector.end(),
                          [propagator] ( const std::set<std::string>& s ) 
                          { return s.find(propagator) != s.end() ; } ) ;

if( iter != clauseVector.end() )
{
    std::cout << "FOUND: " << propagator << "\n";
    clauseVector.erase(iter) ;
}

[Snnnider]

Propagator is an int, sorry should have said previously

Edit: I tweaked it, and now it works! It will however only delete one instance of propagator, is there anyway to run this as many times as needed to delete all instance of propagator?

Thank you

[ne555]

> I tweaked it, and now it works! It will however only delete one instance of propagator
show updated code.

http://www.cplusplus.com/forum/general/129501/#msg699308
Suppose that you've got {&, &, *, *, &} where '*' indicates sets to be erased.
when j=2, you find the first *, and erase it. The resultant vector is {&, &, *, &}
you then increment j, so j=3, find an & and continue.

[Snnnider]

Ahhhh I see, I don't know why I took that for loop out, this is the updated code, which so far seems to be working

for(int j = 0; j < clauseVector.size(); ++j){
  auto iter = std::find_if(clauseVector.begin(), clauseVector.end(),[propagator]     (const std::set<int> & s){
    return s.find(propagator) != s.end();
    });
  (iter != clauseVector.end()){
    std::cout << "Found: " << propagator << "\n";
    clauseVector.erase(iter);
    }
  }

I apologise for formatting, I am no use at formatting on here

Edit: After running on a larger file, this is very slow

[JLBorges]

> It will however only delete one instance of propagator,
> is there anyway to run this as many times as needed to delete all instance of propagator?

>> After running on a larger file, this is very slow

The erase-remove idiom is canonical. http://en.wikipedia.org/wiki/Erase-remove_idiom

auto iter = std::remove_if( clauseVector.begin(), clauseVector.end(),
                            [propagator] ( const std::set<int>& s ) 
                            { return s.find(propagator) != s.end() ; } ) ;

clauseVector.erase( iter, clauseVector.end() ) ;

[Snnnider]

Wow that certainly speeds things up a lot!

Thank you very much!

One step closer to finishing this Unit Clause Propagation algorithm