如何在迭代时从 std::set 中删除元素

2022-01-07 00:00:00 set coding-style c++ stl

如何在迭代时从 std::set 中删除元素

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 stuff
    if(/*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;
   }
}

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