set和multiset区别

#include <iostream>
#include <set>
#include <algorithm>
using namespace std;

class Print
{
public:
   void operator()(int i)
   {
      cout << i << endl;
   }
};

int main()
{
   set<int> s;
   pair<set<int>::iterator, bool> ret = s.insert(3);
   if(ret.second == true)
   {
      cout << "插入成功" << endl;
   }
   else
   {
      cout << "插入失败" << endl;
   }

   ret = s.insert(3);
   if(ret.second == true)
   {
      cout << "插入成功" << endl;
   }
   else
   {
      cout << "插入失败" << endl;
   }

   cout << "--------" << endl;

   multiset<int> ms;
   ms.insert(3);
   ms.insert(3);
   for_each(ms.begin(), ms.end(), Print());

   return 0;
}

$ ./a.out         
插入成功
插入失败
--------
3
3