怎样取出set容器里的这俩个元素?

王二蛋

我想把 set容器里的第一个元素和最后一个元素取出来放入set1容器,但是,用下面这段程序,错误在指在stringIter1 = stringSet.end() - 1;这一句.请大家指点一下.谢谢.
    set<string>::iterator stringIter1;
    stringIter1 = stringSet.begin();
    stringSet1.insert(*stringIter1);
    stringIter1 = stringSet.end() - 1;
    stringSet1.insert(*stringIter1);



下面是错误提示:
--------------------Configuration: 28X3RSQG - Win32 Debug--------------------
Compiling...
28X3RSQGDlg.cpp
D:\Program Files\Microsoft Visual Studio\MyProjects\28X3RSQG\28X3RSQGDlg.cpp(230) : error C2676: binary '-' : 'class std::_Tree<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >,class std::basic_string<char,stru
ct std::char_traits<char>,class std::allocator<char> >,struct std::set<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >,struct std::less<class std::basic_string<char,struct std::char_traits<char>,class std::all
ocator<char> > >,class std::allocator<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > > >::_Kfn,struct std::less<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > >,class
std::allocator<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > > >::iterator' does not define this operator or a conversion to a type acceptable to the predefined operator
Error executing cl.exe.

28X3RSQG.exe - 1 error(s), 0 warning(s)

lenovo

stringSet.end() - 1;
你查查c++教材这样减1语法上正不正确，
允不允许。遇到问题首先应该想到自己
找资料解决。

whyglinux

因为set的iterator不支持随机访问，所以不能对set的iterator进行加减运算。

但是所有的iterator都支持 ++、-- 运算，所以可通过iterator的自加或者自减运算来遍历容器。

对于楼主的程序，可进行下列修改来达到目的：

1. 
   
2. // stringIter1 = stringSet.end() - 1;
   
3. stringIter1 = stringSet.end();
   
4. --stringIter1;
   
5. 
   
6. stringSet1.insert(*stringIter1);
   

复制代码

jeffshia

我是一个c++的菜鸟...