在c++ map<int上迭代，list<int>>

Question

当我试图迭代一个map及其列表成员时，我得到了这个错误：

error: 'template<class _Category, class _Tp, class _Distance, class _Pointer, class _Reference> struct std::iterator' used without template parameters
invalid use of qualified-name '<declaration error>::ii'
error: 'ii' was not declared in this scope
error: 'struct std::_Rb_tree_iterator<std::pair<const int, std::list<int, std::allocator<int> > > >' has no member named 'second'
error: 'struct std::_Rb_tree_iterator<std::pair<const int, std::list<int, std::allocator<int> > > >' has no member named 'second'

这是代码(地图之前已正确填充)：

map<int, list<int> >::iterator it; 
list<int>iterator:: ii;

for(it=this->mapName.begin(); it!=this->mapName.end(); ++it){ 

    cout<<(*it).first<<" { ";
    for(ii = (*it).second().begin(); ii!=(*it).second.end(); ++ii){
        cout<<(*ii)<<" ";
    }
    cout << " }" << endl;                   
}

有什么建议吗？

Answer 1

这里有一个语法错误：

 list<int>iterator::

应该是

 list<int>::iterator

另外，

(*it).second().begin()

应该是

(*it).second.begin()

Answer 2

您可以使用以下命令删除内部for循环-

    std::copy( it->second.begin(), it->second.end(),
               std::ostream_iterator<int>(std::cout, " ") );

这也意味着您可以去掉ii的声明。

Answer 3

map<int, list<int> >::iterator it; 
list<int>::iterator ii;

for(it=this->mapName.begin(); it!=this->mapName.end(); ++it){ 

    cout<<(*it).first<<" { ";
    for(ii = (*it).second.begin(); ii!=(*it).second.end(); ++ii){
        cout<<(*ii)<<" ";
    }
    cout << " }" << endl;                   
}