Advantages of unique_ptr over auto_ptr?

I don't fully understand the benefits unique_ptr

over auto_ptr

, or I'm not completely convinced yet why we need to use unique_ptr

.

I see the following differences.

1) unique_ptr

supports arrays and hence the destructor unique_ptr

calls delete []

for arrays whereas the destructor auto_ptr

only calls delete

.

2) std::move()

should be used instead of direct copy in case unique_ptr

. But what advantage do we get with help std::move()

? I will try to explain as shown below.

auto_ptr <int> p1 (new int);
auto_ptr <int> p2 = p1;    // Now p1 is NULL and p2 exists with value of p1

unique_ptr <int> p1 (new int);
unique_ptr <int> p2 = std::move(p1);    // Now p1 is NULL and p2 exists with value of p1

      

        
        
        
      

    

So what is the advantage we are going to get with this?

3) I read on the internet what unique_ptr

can be used in containers. But if I understood correctly, this is not very good for unique_ptr

. The semantics of the container function changes so that now days, copying is not done inside the container functions. But how is this great thing unique_ptr

? Now that the container functions have changed, why can't we use auto_ptr

in containers?