std::is_sorted
Defined in header <algorithm>
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(1) | ||
template< class ForwardIt > bool is_sorted( ForwardIt first, ForwardIt last ); |
(since C++11) (until C++20) |
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template< class ForwardIt > constexpr bool is_sorted( ForwardIt first, ForwardIt last ); |
(since C++20) | |
template< class ExecutionPolicy, class ForwardIt > bool is_sorted( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last ); |
(2) | (since C++17) |
(3) | ||
template< class ForwardIt, class Compare > bool is_sorted( ForwardIt first, ForwardIt last, Compare comp ); |
(since C++11) (until C++20) |
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template< class ForwardIt, class Compare > constexpr bool is_sorted( ForwardIt first, ForwardIt last, Compare comp ); |
(since C++20) | |
template< class ExecutionPolicy, class ForwardIt, class Compare > bool is_sorted( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last, Compare comp ); |
(4) | (since C++17) |
Checks if the elements in range [first, last)
are sorted in non-descending order.
operator<
.comp
.policy
. These overloads do not participate in overload resolution unless std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is trueParameters
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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Return value
true if the elements in the range are sorted in ascending order
Complexity
linear in the distance between first
and last
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.
Possible implementation
First version |
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template<class ForwardIt> bool is_sorted(ForwardIt first, ForwardIt last) { return std::is_sorted_until(first, last) == last; } |
Second version |
template<class ForwardIt, class Compare> bool is_sorted(ForwardIt first, ForwardIt last, Compare comp) { return std::is_sorted_until(first, last, comp) == last; } |
Notes
std::is_sorted and std::is_sorted_until both return true for empty ranges and ranges of length one.
Example
#include <iostream> #include <algorithm> #include <iterator> int main() { int digits[] = {3, 1, 4, 1, 5}; for (auto i : digits) std::cout << i << ' '; std::cout << ": is_sorted: " << std::boolalpha << std::is_sorted(std::begin(digits), std::end(digits)) << '\n'; std::sort(std::begin(digits), std::end(digits)); for (auto i : digits) std::cout << i << ' '; std::cout << ": is_sorted: " << std::is_sorted(std::begin(digits), std::end(digits)) << '\n'; }
Output:
3 1 4 1 5 : is_sorted: false 1 1 3 4 5 : is_sorted: true
See also
(C++11) |
finds the largest sorted subrange (function template) |