std::list<T,Allocator>::sort

 

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std::list

Member functions
list::list list::~list list::operator= list::assign list::assign_range (C++23)   list::get_allocator Element access list::front list::back Iterators list::beginlist::cbegin (C++11) list::endlist::cend (C++11) list::rbeginlist::crbegin (C++11) list::rendlist::crend (C++11) Capacity list::size list::empty list::max_size	Modifiers list::clear list::insert list::insert_range (C++23) list::emplace (C++11) list::erase list::push_front list::emplace_front (C++11) list::prepend_range (C++23) list::pop_front list::push_back list::emplace_back (C++11) list::append_range (C++23) list::pop_back list::resize list::swap Operations list::merge list::splice list::removelist::remove_if list::reverse list::unique list::sort
Non-member functions
operator==operator<=> (C++20) swap(std::list) erase(std::list)erase_if(std::list) (C++20)(C++20)	operator!=operator<operator>operator<=operator>= (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)
Deduction guides(C++17)

 

void sort();	(1)
template< class Compare > void sort( Compare comp );	(2)

Sorts the elements and preserves the order of equivalent elements. No references or iterators become invalidated.

1) Elements are compared using operator<.

2) Elements are compared using comp.

If an exception is thrown, the order of elements in *this is unspecified.

Parameters

comp	-	comparison function object (i.e. an object that satisfies the requirements of Compare) which returns ​true if the first argument is less than (i.e. is ordered before) the second. The signature of the comparison function should be equivalent to the following: bool cmp(const Type1& a, const Type2& b); While the signature does not need to have const&, the function must not modify the objects passed to it and must be able to accept all values of type (possibly const) Type1 and Type2 regardless of value category (thus, Type1& is not allowed, nor is Type1 unless for Type1 a move is equivalent to a copy(since C++11)). The types Type1 and Type2 must be such that an object of type list<T,Allocator>::const_iterator can be dereferenced and then implicitly converted to both of them. ​
Type requirements
- Compare must meet the requirements of Compare.

Return value

(none)

Complexity

Given \(\scriptsize N\)N as size():

1) Approximately \(\scriptsize N \cdot log(N)\)N·log(N) comparisons using operator<.

2) Approximately \(\scriptsize N \cdot log(N)\)N·log(N) applications of the comparison function comp.

Notes

std::sort requires random access iterators and so cannot be used with list. This function also differs from std::sort in that it does not require the element type of the list to be swappable, preserves the values of all iterators, and performs a stable sort.

Example

Run this code

#include <functional>
#include <iostream>
#include <list>
 
std::ostream& operator<<(std::ostream& ostr, const std::list<int>& list)
{
    for (const int i : list)
        ostr << ' ' << i;
    return ostr;
}
 
int main()
{
    std::list<int> list{8, 7, 5, 9, 0, 1, 3, 2, 6, 4};
    std::cout << "initially: " << list << '\n';
 
    list.sort();
    std::cout << "ascending: " << list << '\n';
 
    list.sort(std::greater<int>());
    std::cout << "descending:" << list << '\n';
}

Output:

initially:  8 7 5 9 0 1 3 2 6 4
ascending:  0 1 2 3 4 5 6 7 8 9
descending: 9 8 7 6 5 4 3 2 1 0

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 1207	C++98	it was unclear whether iterators and/or references will be invalidated	keep valid

See also

reverse

reverses the order of the elements (public member function)