Both return an iterator that designates the first element remaining beyond any elements removed, or end() if no such element exists.
这里没说删除错了会怎么样吧?只是说删除后的返回iterator是指向被删除的元素的之前的那个,如果那个元素不存在,就返回end()吧?
vector::erase
iterator erase(iterator it);
iterator erase(iterator first, iterator last);
The first member function removes the element of the controlled sequence pointed to by it. The second member function removes the elements of the controlled sequence in the range [first, last). Both return an iterator that designates the first element remaining beyond any elements removed, or end() if no such element exists.