std::queue<T,Container>::size

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Diagnostics library

Memory management library

Metaprogramming library (C++11)

General utilities library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library (C++17)

Concurrency support library (C++11)

Execution control library (C++26)

Technical specifications

Symbols index

External libraries

 

Containers library

Sequence

array (C++11)

vector

vector<bool>

inplace_vector (C++26)

hive (C++26)

deque

forward_list (C++11)

list

Associative

set

multiset

map

multimap

Unordered associative

unordered_set (C++11)

unordered_multiset (C++11)

unordered_map (C++11)

unordered_multimap (C++11)

Adaptors

stack

queue

priority_queue

flat_set (C++23)

flat_multiset (C++23)

flat_map (C++23)

flat_multimap (C++23)

Views

span (C++20)

mdspan (C++23)

Tables

Iterator invalidation

Member function table

Non-member function table

 

std::queue

Member functions

queue::queue

queue::~queue

queue::operator=

Element access

queue::front

queue::back

Capacity

queue::empty

queue::size

Modifiers

queue::push

queue::push_range (C++23)

queue::emplace (C++11)

queue::pop

queue::swap (C++11)

Non-member functions

swap(std::queue) (C++11)

operator==operator!=operator<operator>operator<=operator>=operator<=> (C++20)

Helper classes

uses_allocator<std::queue> (C++11)

formatter<std::queue> (C++23)

Deduction guides(C++17)

 

size_type size() const;

Returns the number of elements in the container adaptor. Equivalent to: return c.size().

Parameters

(none)

Return value

The number of elements in the container adaptor.

Complexity

Constant.

Example

Run this code

#include <cassert>
#include <queue>
 
int main()
{
    std::queue<int> queue;
    assert(queue.size() == 0);

    const int count = 8;
    for (int i = 0; i != count; ++i)
        queue.push(i);
    assert(queue.size() == count);
}

See also

empty	checks whether the container adaptor is empty (public member function)
sizessize (C++17)(C++20)	returns the size of a container or array (function template)