c++ vector容器通过迭代器删除元素中奇数问题

Question

vector中的元素{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}。
为什么使用下面的方法可以删除vector容器的偶数

for(auto vbegin = va.begin(); vbegin != va.end(); ++vbegin)
{
    if(!(*vbegin % 2))
    {
        va.erase(vbegin);
    }
}

而当使用类似的方法删除奇数时会报错代码如下，错误提示：Signal: SIGSEGV (Segmentation fault)

for(auto vbegin = va.begin(); vbegin != va.end(); ++vbegin)
    {
        if(*vbegin % 2)
        {
            va.erase(vbegin);
        }
    }

Answer 1

The solution above assigns the iterator to begin() to achieve the effect, but it will restart the traversal every time, reducing efficiency. And another copy iterator will encounter out-of-bounds problems.
This is my plan:

{
    std::vector<int> vec = {1,2,3,4,5,6,7,8,9};
    auto itr = vec.begin();
    while (itr != vec.end()) {
        if (*itr % 2) {
            itr = vec.erase(itr);
        } else {
            itr++;
        }
    }//done
} 

Answer 2

C++ iterators become invalid after erasure,
so the effect of va.erase(vbegin); after ++vbegin is executed is unknown.

It is recommended to define a temporary iterator within the if block to delete container elements

if( any condition about vbegin )
{
    vector<int>::iterator element_to_delete = vbegin;
    ++vbegin;
    va.erase(element_to_delete);
}

Answer 3

Both are wrong, because the iterator will become invalid after the erase call, you need to

va.erase(vbegin);
vbegin = va.begin();

Check the information to find out what happened with erase