从Boost多索引迭代器获取数字索引

#include<iostream>
#include<boost/multi_index_container.hpp>
#include<boost/multi_index/ordered_index.hpp>
#include<boost/multi_index/identity.hpp>
#include<boost/multi_index/member.hpp>

using namespace boost::multi_index;

struct Employee {
    int id;
    std::string name;
    int age;

    Employee(int id, std::string name, int age) : id(id), name(name), age(age) {}
};

typedef multi_index_container<
    Employee,
    indexed_by<
        ordered_unique<identity<Employee>>,
        ordered_non_unique<member<Employee, int, &Employee::id>>,
        ordered_non_unique<member<Employee, std::string, &Employee::name>>,
        ordered_non_unique<member<Employee, int, &Employee::age>>
    >
> EmployeeContainer;

int main() {
    EmployeeContainer employees;
    employees.insert(Employee(1, "Alice", 30));
    employees.insert(Employee(2, "Bob", 25));
    employees.insert(Employee(3, "Charlie", 35));

    auto it = employees.get<1>().find(2);
    if (it != employees.get<1>().end()) {
        std::cout << "Found employee with id 2: " << it->name<< std::endl;
    } else {
        std::cout << "Employee with id 2 not found"<< std::endl;
    }

    return 0;
}