Clear on vector

Question

Refer below code:

Once I clear vector, values are wiped off. Does this mean that allocated memory is also released?

If so, why capacity is also 4 yet after clear ? Is there a way to make it zero again ?
https://code.sololearn.com/cC5QjbKXtawq/?ref=app

Answer 1

After clear the capacity is not changed which means that the allocated memory is not released. To make it zero again you can try using the shrink_to_fit() member function after you call clear()

Answer 2

Agree with Hape,
Also, as I understand it, there is overhead in resizing the internal buffer for bigger size (cmiiw).

So perhaps that is the consideration why `capacity` does not follow `size` after `clear()` was invoked. In anticipation of possible buffer resizing necessity in future, it might be better to still reserve the `capacity`, so there would be less resizing work needed (relatively more efficient).