CODEWITHSUNDEEP
c++iteratorstdset
Roman
Roman

Reputation: 1447

Searching in std::set without iterator C++

I have std::set which contains come int values. Now i use iterator to find out whether set contans value.

But my application use this search very ofter and search using iterator too slow, can i do something like that:

std::set<int> fdsockets;

void myfunc(int fd)
{
    if(fdsockets[fd] != fdsockets.end())
    {
            // my code
    }
}

But i have error when compile using G++

no match for 'operator[]' in 'fdsockets[fd]'

Maybe i can use something instead of std::set?

Thanks!

Upvotes: 3

Views: 393

Answers (4)

hansmaad
hansmaad

Reputation: 18915

std::unorered_set or an ordered vector with binary search are more effective for simple membership test. If the maximum value of intergers is low a lookup table might be an alternative.

Upvotes: 4

Cubbi
Cubbi

Reputation: 47498

If you don't need the iterator that set::find returns (you're just testing existence, not actually going to access the fdsocket), here's an alternative:

if(fdsockets.count(fd))
{
        // my code
}

Upvotes: 0

Benj
Benj

Reputation: 32428

It sounds like you want set::find()

if( fdsockets.find(fd) != fdsockets.end() )
{
      // my code
}

Upvotes: 4

Emilio Garavaglia
Emilio Garavaglia

Reputation: 20759

There is no operator[] in std::set.

You probably mean

if(fdsockets.find(fd) != fdsockets.end())

Upvotes: 2

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