c++ - Qt 中的 STL 迭代器

Question

我想遍历一个列表，删除大于30的元素

QList<double> mylist;
QList<double>::iterator myiterator = mylist.begin();

mylist.append(6);
mylist.append(36);

myiterator=mylist.begin();
while(myiterator!=mylist.end())
{
    if(*(myiterator)>30)
    {
        QList<double>::iterator next=myiterator;
        next++;
        mylist.erase(myiterator);
        myiterator=next;

    }
    else
        myiterator++;

    if(myiterator==mylist.end())
        std::cout<<"end of list "<<std::endl;
    else
        std::cout<<" not end of list "<<std::endl;
}

输出是

 not end of list 
 not end of list 
The program has unexpectedly finished.
/home/maverik/Desktop/Qt/container_class/container_class exited with code 0

如果我让 mylist = {36,34} 或 mylist = {36,9} 或 mylist={9,10} 那么输出是

 not end of list 
end of list 

仅当最后一个元素大于 30 或大于但第一个元素也大于 30 时才会出现错误

Answer 1

像 C++ 标准容器 erase 返回一个迭代器到被删除元素之后的元素，所以你的循环部分应该非常简单:

 if((*myiterator)>30)
    myiterator = mylist.erase( myiterator );
 else
    myiterator++;