STL

set/unordered_set

//set
#include <iostream>
#include <cstdio>
#include <set>
#include <unordered_set>

using namespace std;

#define set unordered_set

int main()
{
    set<int> S;
    for (int i = 0; i < 5; i++)
        S.insert(i);
    //cout << S.begin() << endl;

    for (set<int>::iterator i = S.begin(); i != S.end(); i++)
        cout << *i << " ";
    cout << endl;

    cout <<"Size: "<< S.size() << endl;
    cout << "max size: " << S.max_size() << endl;
    //set<char> s;
    //cout << s.max_size() << endl;
    cout << *S.begin() << endl;
    cout << *(--S.end()) << endl;
    cout << "--------------------" << endl;
    S.clear();
    cout << S.size() << endl;
    //S.insert(1);
    if (S.empty())  cout << "empty" << endl;
    else cout << "No" << endl;
    cout << "--------------------" << endl;
    S.insert(1);
    S.insert(2);
    S.insert(2);//set中元素不能重复
    for (set<int>::iterator i = S.begin(); i != S.end(); i++)
        cout << *i << " ";
    cout << endl;
    cout << S.count(1) << " " << S.count(2) << " " << S.count(0) << endl;
    cout << "--------------------" << endl;
    S.clear();
    int a[] = { 1,2,3,4 };
    set<int> s(a, a + 3);
    set<int>::iterator iter;
    if ((iter = s.find(2)) != s.end())
        cout << *iter << endl;

    if (!(s.find(5) != s.end()))
        cout << "No value" << endl;

    return 0;
}

/*
0 1 2 3 4
Size: 5
max size: 357913941
0
4
--------------------
0
empty
--------------------
1 2
1 1 0
--------------------
2
No value
*/