std::stable_sort - cppreference.com (original) (raw)
Sorts the elements in the range [first, last) in non-descending order. The order of equivalent elements is guaranteed to be preserved.
Elements are sorted with respect to operator<(until C++20)std::less{}(since C++20).
Elements are sorted with respect to comp.
2,4) Same as (1,3), but executed according to policy.
These overloads participate in overload resolution only if all following conditions are satisfied:
If any of the following conditions is satisfied, the behavior is undefined:
Contents
[edit] Parameters
| first, last | - | the pair of iterators defining the range of elements to sort |
|---|---|---|
| policy | - | the execution policy to use |
| 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 RandomIt can be dereferenced and then implicitly converted to both of them. |
| Type requirements | ||
| -RandomIt must meet the requirements of LegacyRandomAccessIterator. | ||
| -Compare must meet the requirements of Compare. |
[edit] Complexity
Given \(\scriptsize N\)N as last - first:
1,2) \(\scriptsize O(N \cdot \log(N))\)O(N·log(N)) comparisons using operator<(until C++20)std::less{}(since C++20) if enough extra memory is available, otherwise \(\scriptsize O(N \cdot \log^{2}(N))\)O(N·log2
(N)) comparisons.
3,4) \(\scriptsize O(N \cdot \log(N))\)O(N·log(N)) applications of the comparator comp if enough extra memory is available, otherwise \(\scriptsize O(N \cdot \log^{2}(N))\)O(N·log2
(N)) applications.
[edit] Exceptions
The overloads with a template parameter named ExecutionPolicy report errors as follows:
- If execution of a function invoked as part of the algorithm throws an exception and
ExecutionPolicyis one of the standard policies, std::terminate is called. For any otherExecutionPolicy, the behavior is implementation-defined. - If the algorithm fails to allocate memory, std::bad_alloc is thrown.
[edit] Possible implementation
See also the implementations in libstdc++ and libc++.
[edit] Notes
This function attempts to allocate a temporary buffer equal in size to the sequence to be sorted. If the allocation fails, the less efficient algorithm is chosen.
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
| __cpp_lib_constexpr_algorithms | 202306L | (C++26) | constexpr stable sorting, overloads (1), (3) |
[edit] Example
#include #include #include #include #include struct Employee { int age; std::string name; // Does not participate in comparisons }; bool operator<(const Employee& lhs, const Employee& rhs) { return lhs.age < rhs.age; } #if __cpp_lib_constexpr_algorithms >= 202306L consteval auto get_sorted() { auto v = std::array{3, 1, 4, 1, 5, 9}; std::stable_sort(v.begin(), v.end()); return v; } static_assert(std::ranges::is_sorted(get_sorted())); #endif int main() { std::vector v{{108, "Zaphod"}, {32, "Arthur"}, {108, "Ford"}}; std::stable_sort(v.begin(), v.end()); for (const Employee& e : v) std::cout << e.age << ", " << e.name << '\n'; }
Output:
32, Arthur 108, Zaphod 108, Ford
[edit] See also
| | sorts a range into ascending order (function template) [edit] | | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | sorts the first N elements of a range (function template) [edit] | | | divides elements into two groups while preserving their relative order (function template) [edit] | | | sorts a range of elements while preserving order between equal elements(algorithm function object)[edit] |