std::minmax_element
Defined in header
<algorithm>
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(1) | ||
template< class ForwardIt >
std::pair<ForwardIt,ForwardIt> |
(since C++11) (until C++17) |
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template< class ForwardIt >
constexpr std::pair<ForwardIt,ForwardIt> |
(since C++17) | |
template< class ExecutionPolicy, class ForwardIt >
constexpr std::pair<ForwardIt,ForwardIt> |
(2) | (since C++17) |
(3) | ||
template< class ForwardIt, class Compare >
std::pair<ForwardIt,ForwardIt> |
(since C++11) (until C++17) |
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template< class ForwardIt, class Compare >
constexpr std::pair<ForwardIt,ForwardIt> |
(since C++17) | |
template< class ExecutionPolicy, class ForwardIt, class Compare >
constexpr std::pair<ForwardIt,ForwardIt> |
(4) | (since C++17) |
Finds the smallest and greatest element in the range [first, last)
.
operator<
.comp
.policy
. These overloads do not participate in overload resolution unless std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true
Contents |
[edit] Parameters
first, last | - | forward iterators defining the range to examine |
policy | - | the execution policy to use. See execution policy for details. |
cmp | - | comparison function object (i.e. an object that satisfies the requirements of Compare ) which returns true if if *a is less than *b . The signature of the comparison function should be equivalent to the following: bool cmp(const Type1 &a, const Type2 &b); The signature does not need to have const &, but the function object must not modify the objects passed to it. |
Type requirements | ||
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ForwardIt must meet the requirements of ForwardIterator .
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[edit] Return value
a pair consisting of an iterator to the smallest element as the first element and an iterator to the greatest element as the second. Returns std::make_pair(first, first) if the range is empty. If several elements are equivalent to the smallest element, the iterator to the first such element is returned. If several elements are equivalent to the largest element, the iterator to the last such element is returned.
[edit] Complexity
At most max(floor(3/2(N−1)), 0) applications of the predicate, where N = 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,
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- if
policy
is std::parallel_vector_execution_policy, std::terminate is called - if
policy
is std::sequential_execution_policy or std::parallel_execution_policy, the algorithm exits with an std::exception_list containing all uncaught exceptions. If there was only one uncaught exception, the algorithm may rethrow it without wrapping in std::exception_list. It is unspecified how much work the algorithm will perform before returning after the first exception was encountered. - if
policy
is some other type, the behavior is implementation-defined
- if
- If the algorithm fails to allocate memory (either for itself or to construct an std::exception_list when handling a user exception), std::bad_alloc is thrown.
[edit] Notes
This algorithm is different from std::make_pair(std::min_element(), std::max_element()), not only in efficiency, but also in that this algorithm finds the last biggest element while std::max_element finds the first biggest element.
[edit] Possible implementation
First version |
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Second version |
template<class ForwardIt, class Compare> std::pair<ForwardIt, ForwardIt> minmax_element(ForwardIt first, ForwardIt last, Compare comp) { std::pair<ForwardIt, ForwardIt> result(first, first); if (first == last) return result; if (++first == last) return result; if (comp(*first, *result.first)) { result.first = first; } else { result.second = first; } while (++first != last) { ForwardIt i = first; if (++first == last) { if (comp(*i, *result.first)) result.first = i; else if (!(comp(*i, *result.second))) result.second = i; break; } else { if (comp(*first, *i)) { if (comp(*first, *result.first)) result.first = first; if (!(comp(*i, *result.second))) result.second = i; } else { if (comp(*i, *result.first)) result.first = i; if (!(comp(*first, *result.second))) result.second = first; } } } return result; } |
[edit] Example
#include <algorithm> #include <iostream> #include <vector> int main() { std::vector<int> v = { 3, 9, 1, 4, 2, 5, 9 }; auto result = std::minmax_element(v.begin(), v.end()); std::cout << "min element at: " << (result.first - v.begin()) << '\n'; std::cout << "max element at: " << (result.second - v.begin()) << '\n'; }
Output:
min element at: 2 max element at: 6
[edit] See also
returns the smallest element in a range (function template) |
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returns the largest element in a range (function template) |
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(parallelism TS)
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parallelized version of std::minmax_element (function template) |