std::is_partitioned
From cppreference.com
Defined in header
<algorithm>
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template< class InputIt, class UnaryPredicate >
bool is_partitioned( InputIt first, InputIt last, UnaryPredicate p ); |
(since C++11) | |
Returns true if all elements in the range [first, last)
that satisfy the predicate p
appear before all elements that don't. Also returns true if [first, last)
is empty.
Contents |
[edit] Parameters
first, last | - | the range of elements to check |
p | - | unary predicate which returns true for the elements expected to be found in the beginning of the range. The signature of the predicate function should be equivalent to the following: bool pred(const Type &a); The signature does not need to have const &, but the function must not modify the objects passed to it. |
Type requirements | ||
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InputIt must meet the requirements of InputIterator .
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UnaryPredicate must meet the requirements of Predicate .
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[edit] Return value
true if the range [first, last)
is empty or is partitioned by p
. false otherwise.
[edit] Complexity
At most std::distance(first, last)
applications of p
.
[edit] Possible implementation
template< class InputIt, class UnaryPredicate > bool is_partitioned(InputIt first, InputIt last, UnaryPredicate p) { for (; first != last; ++first) if (!p(*first)) break; for (; first != last; ++first) if (p(*first)) return false; return true; } |
[edit] Example
Run this code
#include <algorithm> #include <array> #include <iostream> int main() { std::array<int, 9> v = { 1, 2, 3, 4, 5, 6, 7, 8, 9 }; auto is_even = [](int i){ return i % 2 == 0; }; std::cout.setf(std::ios_base::boolalpha); std::cout << std::is_partitioned(v.begin(), v.end(), is_even) << ' '; std::partition(v.begin(), v.end(), is_even); std::cout << std::is_partitioned(v.begin(), v.end(), is_even) << ' '; std::reverse(v.begin(), v.end()); std::cout << std::is_partitioned(v.begin(), v.end(), is_even); }
Output:
false true false
[edit] See also
divides a range of elements into two groups (function template) |
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(C++11)
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locates the partition point of a partitioned range (function template) |
(parallelism TS)
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parallelized version of std::is_partitioned (function template) |