加了&代表引用,如果不加,则是值拷贝
#include <iostream>
#include <set>
using namespace std;
int main()
{
// cbegin/cend(c++11): Returns a const_iterator pointing to the first element in the container/
// Returns a const_iterator pointing to the past-the-end element in the container
std::set<int> myset = { 50, 20, 60, 10, 25 };
std::cout << "myset contains:";
for (auto it:myset)
std::cout << ' ' << it;
std::cout << '\n';
std::cout << "myset contains:";
for (auto &it:myset)
std::cout << ' ' << it;
system("pause");
return 0;
}