#include <iostream>
#include <map>
using namespace std;
map<int, int> mp;

int main() {
    mp[50] = 2;
    mp[30] = 6;
    mp[10] = 1;
    cout << mp.size() << endl;
    // 遍历
    for (auto [k, v] : mp) {
        cout << k << ' ' << v << endl;
    }
    // 迭代
    cout << "iterator: " << endl;
    for (map<int, int>::iterator it = mp.begin(); it != mp.end(); it++) {
        cout << (*it).first << "," << (*it).second << endl;   
    }
    for (auto it = mp.begin(); it != mp.end(); it++) {
        cout << (*it).first << "," << (*it).second << endl;   
    }
    // 倒序遍历 map<int, int>::reverse_iterator
    cout << "reverse_iterator:" << endl;
    for (map<int, int>::reverse_iterator rit = mp.rbegin(); rit != mp.rend(); rit++) {
        cout << (*rit).first << "," << (*rit).second << endl;   
    }
    cout << "倒序遍历:" << endl;
    for (auto rit = mp.rbegin(); rit != mp.rend(); rit++) {
        cout << (*rit).first << "," << (*rit).second << endl;   
    }
    return 0;
}