【原创】C++STL multiset

资料来源：官方文档

multiset是一个按照特定排序储存元素的容器，多个元素可以有相同的值。元素的值即为其本身的键值。multiset中的值无法修改，可插入删除。常用于实现二叉树。

定义一个multiset:

 // constructing multisets
 #include <iostream>
 #include <set>
 using namespace std;
 bool fncomp (int lhs, int rhs) {return lhs<rhs;}

 struct classcomp {
   bool operator() (const int& lhs, const int& rhs) const
   {return lhs<rhs;}
 };

 int main ()
 {
   multiset<int> first;                          //基本定义

   int myints[]= {,,,,};
   multiset<int> second (myints,myints+);       // pointers used as iterators

   multiset<int> third (second);                 // 复制

   multiset<int> fourth (second.begin(), second.end());  // iterator ctor.

   multiset<int,classcomp> fifth;                // class as Compare

   bool(*fn_pt)(int,int) = fncomp;
   multiset<int,bool(*)(int,int)> sixth (fn_pt); // function pointer as Compare

   return ;
 }

容器间赋值：

 // assignment operator with multisets
 #include <iostream>
 #include <set>

 int main ()
 {
   int myints[]={ ,,,, };
   std::multiset<int> first (myints,myints+);   // multiset with 5 ints
   std::multiset<int> second;                    // empty multiset

   second=first;                                 // now second contains the 5 ints
   first=std::multiset<int>();                   // 清空first

   std::cout << "Size of first: " << first.size() << '\n';
   std::cout << "Size of second: " << second.size() << '\n';
   return ;
 }

输出为：

 Size of first:
 Size of second: 

遍历容器：

int main ()
{
  int myints[] = {,,,,};
  multiset<int> mymultiset (myints,myints+);

  multiset<int>::iterator it;//定义一个在multiset上的iterator

  cout << "mymultiset contains:";
  for (multiset<int>::iterator it=mymultiset.begin(); it!=mymultiset.end(); ++it)
    cout << ' ' << *it;

  cout << '\n';

  return ;
}

输出：

mymultiset contains:     

插入操作：

int main ()
{
  multiset<int> mymultiset;
  multiset<int>::iterator it;

  // set some initial values:
  for (int i=; i<=; i++) mymultiset.insert(i*);  // 10 20 30 40 50

  it=mymultiset.insert();

  it=mymultiset.insert (it,);    // max efficiency inserting
  it=mymultiset.insert (it,);    // max efficiency inserting
  it=mymultiset.insert (it,);    // no max efficiency inserting (24<29)

  int myints[]= {,,};
  mymultiset.insert (myints,myints+);

  cout << "mymultiset contains:";
  for (it=mymultiset.begin(); it!=mymultiset.end(); ++it)
    cout << ' ' << *it;
  cout << '\n';

  return ;
}

输出：

myset contains:            

删除某个特定元素：

 int main ()
 {
   std::multiset<int> mymultiset;
   std::multiset<int>::iterator it;

   // insert some values:
   mymultiset.insert ();                            //
   for (int i=; i<; i++) mymultiset.insert(i*);   // 10 20 30 40 40 50 60

   it=mymultiset.begin();
   it++;                                              //    ^

   mymultiset.erase (it);                             // 10 30 40 40 50 60

   mymultiset.erase ();                             // 10 30 50 60

   it=mymultiset.find ();
   mymultiset.erase ( it, mymultiset.end() );         // 10 30

   cout << "mymultiset contains:";
   for (it=mymultiset.begin(); it!=mymultiset.end(); ++it)
    cout << ' ' << *it;
   cout << '\n';

   return ;
 }

清空容器：

 multiset<int> list;
 list.clear();