std::is_sorted
Defined in header <algorithm>
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template< class ForwardIt > bool is_sorted( ForwardIt first, ForwardIt last ); |
(1) | (since C++11) (constexpr since C++20) |
template< class ExecutionPolicy, class ForwardIt > bool is_sorted( ExecutionPolicy&& policy, |
(2) | (since C++17) |
template< class ForwardIt, class Compare > bool is_sorted( ForwardIt first, ForwardIt last, Compare comp ); |
(3) | (since C++11) (constexpr since C++20) |
template< class ExecutionPolicy, class ForwardIt, class Compare > bool is_sorted( ExecutionPolicy&& policy, |
(4) | (since C++17) |
Checks if the elements in range [
first,
last)
are sorted in non-descending order.
std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true. |
(until C++20) |
std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>> is true. |
(since C++20) |
Contents |
[edit] Parameters
first, last | - | the range of elements to examine |
policy | - | the execution policy to use. See execution policy for details. |
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) |
Type requirements | ||
-ForwardIt must meet the requirements of LegacyForwardIterator.
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-Compare must meet the requirements of Compare.
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[edit] Return value
true if the elements in the range are sorted in non-descending order, false otherwise.
[edit] Complexity
Given N as std::distance(first, last):
[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
ExecutionPolicy
is 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++.
is_sorted (1) |
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template<class ForwardIt> bool is_sorted(ForwardIt first, ForwardIt last) { return std::is_sorted_until(first, last) == last; } |
is_sorted (3) |
template<class ForwardIt, class Compare> bool is_sorted(ForwardIt first, ForwardIt last, Compare comp) { return std::is_sorted_until(first, last, comp) == last; } |
[edit] Notes
std::is_sorted
returns true for empty ranges and ranges of length one.
[edit] Example
#include <algorithm> #include <cassert> #include <functional> #include <iterator> #include <vector> int main() { std::vector<int> v; assert(std::is_sorted(v.cbegin(), v.cend()) && "an empty range is always sorted"); v.push_back(42); assert(std::is_sorted(v.cbegin(), v.cend()) && "a range of size 1 is always sorted"); int data[] = {3, 1, 4, 1, 5}; assert(not std::is_sorted(std::begin(data), std::end(data))); std::sort(std::begin(data), std::end(data)); assert(std::is_sorted(std::begin(data), std::end(data))); assert(not std::is_sorted(std::begin(data), std::end(data), std::greater<>{})); }
[edit] See also
(C++11) |
finds the largest sorted subrange (function template) |
(C++20) |
checks whether a range is sorted into ascending order (algorithm function object) |