对码当歌,猿生几何?

std::stack::size

From cppreference.com
< cpp‎ | container‎ | stack

size_type size() const;

Returns the number of elements in the underlying container, that is, c.size().

Parameters

(none)

Return value

The number of elements in the container.

Complexity

Constant.

See also

checks whether the underlying container is empty
(public member function)