How can I remove elements from an std::set while iterating over it
我的第一次尝试看起来像:
My first attempt looks like:
set<T> s;
for(set<T>::iterator iter = s.begin(); iter != s.end(); ++iter) {
//Do some stuffif(/*some condition*/)
s.erase(iter--);
}
但是如果我们想从集合中删除第一个元素，这是有问题的，因为 iter-- 使迭代器无效.
But this is problematic if we want to remove the first element from the set because iter-- invalidates the iterator.
执行此操作的标准方法是什么?
What's the standard way to do this?
推荐答案
标准方式是做类似的事情
Standard way is to do something like
for(set<T>::iterator iter = s.begin(); iter != s.end();)
{
if(/*some condition*/)
{
s.erase(iter++);
}
else
{
++iter;
}
}
根据第一个条件，我们可以确定 iter 无论如何都不会失效，因为 iter 的副本将被传递到 erase，但是我们的 iter 在调用擦除之前已经递增.
By the first condition we are sure, that iter will not be invalidated anyway, since a copy of iter will be passed into erase, but our iter is already incremented, before erase is called.
在 C++11 中，代码类似于
In C++11, the code will be like
for(set<T>::iterator iter = s.begin(); iter != s.end();)
{
if(/*some condition*/)
{
iter = s.erase(iter);
}
else
{
++iter;
}
}
