std::is_sorted_until
Defined in header <algorithm>
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(1) | ||
template< class ForwardIt > ForwardIt is_sorted_until( ForwardIt first, ForwardIt last ); |
(since C++11) (until C++20) |
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template< class ForwardIt > constexpr ForwardIt is_sorted_until( ForwardIt first, ForwardIt last ); |
(since C++20) | |
template< class ExecutionPolicy, class ForwardIt > ForwardIt is_sorted_until( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last ); |
(2) | (since C++17) |
(3) | ||
template< class ForwardIt, class Compare > ForwardIt is_sorted_until( ForwardIt first, ForwardIt last, |
(since C++11) (until C++20) |
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template< class ForwardIt, class Compare > constexpr ForwardIt is_sorted_until( ForwardIt first, ForwardIt last, |
(since C++20) | |
template< class ExecutionPolicy, class ForwardIt, class Compare > ForwardIt is_sorted_until( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last, |
(4) | (since C++17) |
Examines the range [first, last)
and finds the largest range beginning at first
in which the elements are sorted in ascending 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
The upper bound of the largest range beginning at first
in which the elements are sorted in ascending order. That is, the last iterator it
for which range [first, it)
is sorted.
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> ForwardIt is_sorted_until(ForwardIt first, ForwardIt last) { return is_sorted_until(first, last, std::less<>()); } |
Second version |
template <class ForwardIt, class Compare> ForwardIt is_sorted_until(ForwardIt first, ForwardIt last, Compare comp) { if (first != last) { ForwardIt next = first; while (++next != last) { if (comp(*next, *first)) return next; first = next; } } return 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> #include <random> int main() { std::random_device rd; std::mt19937 g(rd()); const int N = 6; int nums[N] = {3, 1, 4, 1, 5, 9}; const int min_sorted_size = 4; int sorted_size = 0; do { std::shuffle(nums, nums + N, g); int *sorted_end = std::is_sorted_until(nums, nums + N); sorted_size = std::distance(nums, sorted_end); for (auto i : nums) std::cout << i << ' '; std::cout << " : " << sorted_size << " initial sorted elements\n"; } while (sorted_size < min_sorted_size); }
Possible output:
4 1 9 5 1 3 : 1 initial sorted elements 4 5 9 3 1 1 : 3 initial sorted elements 9 3 1 4 5 1 : 1 initial sorted elements 1 3 5 4 1 9 : 3 initial sorted elements 5 9 1 1 3 4 : 2 initial sorted elements 4 9 1 5 1 3 : 2 initial sorted elements 1 1 4 9 5 3 : 4 initial sorted elements
See also
(C++11) |
checks whether a range is sorted into ascending order (function template) |