std::includes
Defined in header <algorithm>
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template< class InputIt1, class InputIt2 > bool includes( InputIt1 first1, InputIt1 last1, |
(1) | |
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2 > bool includes( ExecutionPolicy&& policy, ForwardIt1 first1, ForwardIt1 last1, |
(2) | (since C++17) |
template< class InputIt1, class InputIt2, class Compare > bool includes( InputIt1 first1, InputIt1 last1, |
(3) | |
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2, class Compare > bool includes( ExecutionPolicy&& policy, ForwardIt1 first1, ForwardIt1 last1, |
(4) | (since C++17) |
Returns true if every element from the sorted range [first2, last2)
is found within the sorted range [first1, last1)
. Also returns true if [first2, last2)
is empty.
comp
.policy
. This overload only participates in overload resolution if std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is trueParameters
first1, last1 | - | the sorted range of elements to examine |
first2, last2 | - | the sorted range of elements to search for |
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); The signature does not need to have const &, but the function object must not modify the objects passed to it. |
Type requirements | ||
-InputIt1, InputIt2 must meet the requirements of InputIterator .
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-ForwardIt1, ForwardIt2 must meet the requirements of ForwardIterator .
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Return value
true if every element from [first2, last2)
is a member of [first, last)
.
Complexity
At most 2·(N1+N2-1) comparisons, where N1 = std::distance(first1, last1) and N2 = std::distance(first2, last2).
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 three 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 InputIt1, class InputIt2> bool includes(InputIt1 first1, InputIt1 last1, InputIt2 first2, InputIt2 last2) { for (; first2 != last2; ++first1) { if (first1 == last1 || *first2 < *first1) return false; if ( !(*first1 < *first2) ) ++first2; } return true; } |
Second version |
template<class InputIt1, class InputIt2> bool includes(InputIt1 first1, InputIt1 last1, InputIt2 first2, InputIt2 last2, Compare comp) { for (; first2 != last2; ++first1) { if (first1 == last1 || comp(*first2, *first1)) return false; if (!comp(*first1, *first2)) ++first2; } return true; } |
Example
#include <iostream> #include <algorithm> #include <cctype> #include <vector> int main() { std::vector<char> v1 {'a', 'b', 'c', 'f', 'h', 'x'}; std::vector<char> v2 {'a', 'b', 'c'}; std::vector<char> v3 {'a', 'c'}; std::vector<char> v4 {'g'}; std::vector<char> v5 {'a', 'c', 'g'}; for (auto i : v1) std::cout << i << ' '; std::cout << "\nincludes:\n" << std::boolalpha; for (auto i : v2) std::cout << i << ' '; std::cout << ": " << std::includes(v1.begin(), v1.end(), v2.begin(), v2.end()) << '\n'; for (auto i : v3) std::cout << i << ' '; std::cout << ": " << std::includes(v1.begin(), v1.end(), v3.begin(), v3.end()) << '\n'; for (auto i : v4) std::cout << i << ' '; std::cout << ": " << std::includes(v1.begin(), v1.end(), v4.begin(), v4.end()) << '\n'; for (auto i : v5) std::cout << i << ' '; std::cout << ": " << std::includes(v1.begin(), v1.end(), v5.begin(), v5.end()) << '\n'; auto cmp_nocase = [](char a, char b) { return std::tolower(a) < std::tolower(b); }; std::vector<char> v6 {'A', 'B', 'C'}; for (auto i : v6) std::cout << i << ' '; std::cout << ": (case-insensitive) " << std::includes(v1.begin(), v1.end(), v6.begin(), v6.end(), cmp_nocase) << '\n'; }
Output:
a b c f h x includes: a b c : true a c : true g : false a c g : false A B C : (case-insensitive) true
See also
computes the difference between two sets (function template) | |
searches for a range of elements (function template) |