std :: list遍历+擦除 [英] std::list traversal+erase
问题描述
嗨
我有一些标准清单，我想要遍历。在遍历期间，我想
有条件地删除一些对象。
我现在的代码就像这样：
for（std :: list< myStruct> :: iterator it = myList.begin（）; it！= myList.end（）;）
{
if（it-> someCondition）
{
std :: list< myStruct> :: iterator it2 = it;
++它;
myList.erase（it2）;
继续;
}
// ..对myStructs做一些不应该被删除的工作
还有......
++ it;
}
我的问题还有更优雅的解决方案吗？这是非常难看的代码
现在imho。
只需使用myList.erase（it ++）;不起作用，因为在擦除行之后，
迭代器不再有效，因此无法再增加。
非常感谢
Hi
I have some std list, I''d like to traverse. During the traversal, I want to
conditionally delete some objects.
My code for that is like this right now:
for (std::list<myStruct>::iterator it=myList.begin();it!=myList.end();)
{
if (it->someCondition)
{
std::list<myStruct>::iterator it2=it;
++it;
myList.erase(it2);
continue;
}
// .. do some work on the myStructs that arent supposed to be deleted
yet...
++it;
}
Is there any more elegant solution for my problem? It''s quite ugly code
right now imho.
Simply using myList.erase(it++); doesnt work because after the erase line,
the iterator isnt valid anymore and thus cant be increased anymore.
Thanks alot
推荐答案
Frank Neuhaus写道：
Frank Neuhaus wrote:
嗨
我有一些标准清单，我我想穿越。在遍历过程中，我希望
有条件地删除一些对象。
我现在的代码是这样的：
for（std :: list< myStruct> :: iterator it = myList.begin（）; it！= myList.end（）;）
{
if（it-> someCondition）
{
std :: list< myStruct> :: iterator it2 = it;
++它;
myList.erase（it2）;
继续;
}
// ..对myStructs做一些不应该被删除的工作
还有......
++ it;
}
我的问题还有更优雅的解决方案吗？这是非常难看的代码
现在imho。
只需使用myList.erase（it ++）;不起作用，因为在擦除行之后，
迭代器不再有效，因此无法再增加。
Hi
I have some std list, I''d like to traverse. During the traversal, I want
to conditionally delete some objects.
My code for that is like this right now:
for (std::list<myStruct>::iterator it=myList.begin();it!=myList.end();)
{
if (it->someCondition)
{
std::list<myStruct>::iterator it2=it;
++it;
myList.erase(it2);
continue;
}
// .. do some work on the myStructs that arent supposed to be deleted
yet...
++it;
}
Is there any more elegant solution for my problem? It''s quite ugly code
right now imho.
Simply using myList.erase(it++); doesnt work because after the erase line,
the iterator isnt valid anymore and thus cant be increased anymore.
只需使用返回的迭代器：
if（it-> someCondition）
{
it = myList.erase（it）;
}
else
{
//做好工作
++ it;
}
Just use the returned iterator:
if (it->someCondition)
{
it = myList.erase(it);
}
else
{
//do the work
++it;
}
Frank Neuhaus写道：
Frank Neuhaus wrote:
嗨
我有一些标准清单，我想要遍历。在遍历期间，我想
有条件地删除一些对象。
Hi
I have some std list, I''d like to traverse. During the traversal, I want to
conditionally delete some objects.
您确定要使用列表吗？ std :: vector（或std :: deque）可能
这里是一个更好的选择。
Are you sure you want to use a list? std::vector (or std::deque) might
well be a better choice here.
>
我现在的代码是这样的：
for（ std :: list< myStruct> :: iterator it = myList.begin（）; it！= myList.end（）;）
{
if（it-> ; someCondition）
{
std :: list< myStruct> :: iterator it2 = it;
++ it;
myList.erase（it2）;
继续;
}
>
My code for that is like this right now:
for (std::list<myStruct>::iterator it=myList.begin();it!=myList.end();)
{
if (it->someCondition)
{
std::list<myStruct>::iterator it2=it;
++it;
myList.erase(it2);
continue;
}
替换为：
if（it-> someCondition）
{
myList.erase（it ++）;
}
else
++ it;
Replace with:
if (it->someCondition)
{
myList.erase(it++);
}
else
++it;
>
// ..对不应删除的myStructs做一些工作
但是...
++它;
}
我的问题是否还有更优雅的解决方案？这是非常难看的代码
现在imho。
只需使用myList.erase（it ++）;不起作用，因为在擦除行之后，
迭代器不再有效，因此无法再增加。
>
// .. do some work on the myStructs that arent supposed to be deleted
yet...
++it;
}
Is there any more elegant solution for my problem? It''s quite ugly code
right now imho.
Simply using myList.erase(it++); doesnt work because after the erase line,
the iterator isnt valid anymore and thus cant be increased anymore.
这是不正确的。它类似于（伪代码）：
迭代器增量（iterator& i）
{
iterator res = i;
i = i + 1;
返回res;
}
所以myList.erase（它++），迭代器在
myList.erase被调用之前递增。
/ Peter
That is not correct. it++ is similar to (pseudocode):
iterator increment(iterator& i)
{
iterator res = i;
i = i + 1;
return res;
}
so in myList.erase(it++), the iterator is incremented before
myList.erase is called.
/Peter
" peter koch" < pe *************** @ gmail.com写信息
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>
Frank Neuhaus写道：
>
Frank Neuhaus wrote:
>嗨
我有一些标准列表，我想遍历。在遍历期间，我希望
有条件地删除一些对象。
>Hi
I have some std list, I''d like to traverse. During the traversal, I want
to
conditionally delete some objects.
您确定要使用列表吗？ std :: vector（或std :: deque）可能
这里是一个更好的选择。
Are you sure you want to use a list? std::vector (or std::deque) might
well be a better choice here.
你是否确定要在他删除这样的元素时推荐一个向量
？似乎
给我一个列表是更好的选择。
擦除后的增量其他预增量
idiom不会在矢量上工作。
Are you sure that you want to recommend a vector
when he''s erasing elements like this? Seems
to me that a list is a better choice given that.
The post increment on erase else pre increment
idiom won''t work on a vector.
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