关联容器set, multiset

#include <iostream>
#include <set>

using namespace std;

template <class T>
void Print(T first, T last)
{
    for (; first != last; first++)
    {
        cout << *(first) << " ";
    }
    cout << endl;
}
class A
{
private:
    int n;
public:
    A(int _n) :n(_n) {};
    friend bool operator<(const A & a1, const A& a2)
    {
        return a1.n < a2.n;    
    }
    friend ostream & operator<<(ostream & o,const A &a)
    {
        o << a.n;
        return o;
    }
    friend class Myclass;
};
struct Myclass
{
    bool operator()(const A & a1, const A & a2)
    {
        return (a1.n % 10 < a2.n % 10);
    }
};

typedef multiset<A> Mset1;
typedef multiset<A, Myclass> Mset2;//重新定义排序

int main()
{
    const int size = 6;
    A a[size] = { 1, 12, 9, 20, 89 ,78};
    Mset1 m1;
    m1.insert(a, a + size);
    Print(m1.begin(), m1.end());
    m1.insert(20);
    cout << "inserted the number:20" << endl;
    Print(m1.begin(),m1.end());
    Mset1::iterator it;
    it = m1.find(20);
    m1.erase(it);
    cout << "deleted the number:20" << endl;
    Print(m1.begin(), m1.end());
    Mset2 m2;
    m2.insert(m1.begin(), m1.end());
    cout << "the multiset m2 is :" << endl;
    Print(m2.begin(), m2.end());
    return 0;
}

#include <iostream>
#include <set>
using namespace std;
int main() {
typedef set<int>::iterator IT;
int a[5] = { 3,4,6,1,2 };
set<int> st(a,a+5); // st里是 1 2 3 4 6
pair< IT,bool> result;
result = st.insert(5); // st变成 1 2 3 4 5 6
if( result.second ) //插入成功则输出被插入元素
cout << * result.first << " inserted" << endl; //输出: 5 inserted
if( st.insert(5).second ) cout << * result.first << endl;
else
cout << * result.first << " already exists" << endl; //输出 5 already exists
pair<IT,IT> bounds = st.equal_range(4);
cout << * bounds.first << "," << * bounds.second ; //输出：4,5
return 0;
}