In std::multiset is there a function or algorithm to erase just one sample (unicate or duplicate) if an element is found

问题

Perhaps this is a duplicate but I did not find anything searching: When erase(value) is called on std::multiset all elements with the value found are deleted. The only solution I could think of is:

std::multiset<int>::iterator hit(mySet.find(5));
if (hit!= mySet.end()) mySet.erase(hit);

This is ok but I thought there might be better. Any Ideas ?

回答1:

auto itr = my_multiset.find(value);
if(itr!=my_multiset.end()){
    my_multiset.erase(itr);
}

I would imagine there is a cleaner way of accomplishing the same. But this gets the job done.

回答2:

Try this one:

multiset<int> s;
s.erase(s.lower_bound(value));

As long as you can ensure that the value exits in the set. That works.

回答3:

 if(my_multiset.find(key)!=my_multiset.end())
   my_multiset.erase(my_multiset.equal_range(key).first);

This is the best way i can think of to remove a single instance in a multiset in c++

回答4:

I would try the following.

First call equal_range() to find the range of elements that equal to the key.

If the returned range is non-empty, then erase() a range of elements (i.e. the erase() which takes two iterators) where:

the first argument is the iterator to the 2nd element in the returned range (i.e. one past .first returned) and
the second argument as the returned range pair iterator's .second one.

Edit after reading templatetypedef's (Thanks!) comment:

If one (as opposed to all) duplicate is supposed to be removed: If the pair returned by equal_range() has at least two elements, then erase() the first element by passing the the .first of the returned pair to single iterator version of the erase():

Pseudo-code:

pair<iterator, iterator> pit = mymultiset.equal_range( key );

if( distance( pit.first, pit.second ) >= 2 ) {
    mymultiset.erase( pit.first );
}

回答5:

We can do something like this:

multiset<int>::iterator it, it1;
it = myset.find(value);
it1 = it;
it1++;
myset.erase (it, it1);

回答6:

In fact, the correct answer is:

my_multiset.erase(my_multiset.find(value));

来源：https://stackoverflow.com/questions/9167745/in-stdmultiset-is-there-a-function-or-algorithm-to-erase-just-one-sample-unic

标签

c++

stl

multiset