If it's linked list, why doesn't it support push\_back?

If it's simply array, why does it need linear time when accessed by subscript?

Appreciated for your help.

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Edit: We can append element in front of a list like this `1:[2,3]`, that's push\_front; but we can't do it this way: `[2,3]:4`, that's push\_back.

ps. actually I borrow push\_front/back from C++'s STL