template & lt; Typename T> 
The class Queue 
{
Private: 
Struct Node 
{
T data_; 
STD: : unique_ptr & lt; Node> Next_; 
Data Node (T) : data_ (STD: : move (data)) {} 
}; 
STD: : unique_ptr & lt; Node> Head_ {nullptr}; 
Node * tail_ {nullptr}; 
Public: 
STD: : from & lt; T> Try_pop () 
{
If (head_==nullptr) 
Return STD: : from & lt; T> (a); 
STD: : from & lt; T> Res (STD: : make_shared & lt; T> (STD: : move (head_ - & gt; Data_))); 
//STD: : unique_ptr & lt; Node> Old_head=STD: : move (head_); 
//head_=STD: : move (old_head_ - & gt; Next_); 
Head_=STD: : move (head_ - & gt; Next_); 
return res; 
} 
} 

notes at the bottom of the local head first release would happen

CodePudding user response:

No, you should check whether old_head_ is nullptr, if for nullptr old_head_ - & gt; Next_ complains