Unique elements problem

[gouqizi.lvcha]

Hi all

I have a large vector with float point numbers in it, for example
(1.1, 2.1 , 3.2 , 3.3 , 4, 6, 3.2, 8). Is there an easy way to
determine
how many uique elements in the array?

Thanks

Rick

 

[Rapscallion]

I have a large vector with float point numbers in it, for example
(1.1, 2.1 , 3.2 , 3.3 , 4, 6, 3.2, 8). Is there an easy way to
determine how many uique elements in the array?

1. copy vector(*)
2. std::sort()
3. std::unique

(*) you must copy the vector because std::unique deletes/overwrites
elements.

 

[Victor Bazarov]

I have a large vector with float point numbers in it, for example
(1.1, 2.1 , 3.2 , 3.3 , 4, 6, 3.2, 8). Is there an easy way to
determine
how many uique elements in the array?

Have you looked at 'std::unique'? It's mutating, so you might want
to make a copy of your array (unless you don't care that it's going
to re-sort them).

V

 

[Clem.Dickey]

1. copy vector(*)
2. std::sort()
3. std::unique

You can also use a set:

#include <set>
#include <iterator>

template <class F>
typename std::iterator_traits<F>::difference_type
count_unique( F first, F last )
{
typedef typename std::iterator_traits<F>::value_type V;
return std::set<V>( first, last ).size();
};

// ...
std::cout << count_unique( v.begin(), v.end() ) << "\n";