std::find_first_of
Defined in header <algorithm>
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(1) | ||
template< class ForwardIt1, class ForwardIt2 > ForwardIt1 find_first_of( ForwardIt1 first, ForwardIt1 last, |
(until C++11) | |
template< class InputIt, class ForwardIt > InputIt find_first_of( InputIt first, InputIt last, |
(since C++11) (until C++20) |
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template< class InputIt, class ForwardIt > constexpr InputIt find_first_of( InputIt first, InputIt last, |
(since C++20) | |
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2 > ForwardIt1 find_first_of( ExecutionPolicy&& policy, ForwardIt1 first, ForwardIt1 last, |
(2) | (since C++17) |
(3) | ||
template< class ForwardIt1, class ForwardIt2, class BinaryPredicate > ForwardIt1 find_first_of( ForwardIt1 first, ForwardIt1 last, |
(until C++11) | |
template< class InputIt, class ForwardIt, class BinaryPredicate > InputIt find_first_of( InputIt first, InputIt last, |
(since C++11) (until C++20) |
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template< class InputIt, class ForwardIt, class BinaryPredicate > constexpr InputIt find_first_of( InputIt first, InputIt last, |
(since C++20) | |
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2, class BinaryPredicate > ForwardIt1 find_first_of( ExecutionPolicy&& policy, ForwardIt1 first, ForwardIt last, |
(4) | (since C++17) |
Searches the range [first, last)
for any of the elements in the range [s_first, s_last)
.
operator==
.p
.policy
. This overload only participates in overload resolution if std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is trueParameters
first, last | - | the range of elements to examine |
s_first, s_last | - | the range of elements to search for |
policy | - | the execution policy to use. See execution policy for details. |
p | - | binary predicate which returns true if the elements should be treated as equal. The signature of the predicate function should be equivalent to the following: bool pred(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 | ||
-InputIt must meet the requirements of LegacyInputIterator.
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-ForwardIt1 must meet the requirements of LegacyForwardIterator.
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-ForwardIt2 must meet the requirements of LegacyForwardIterator.
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Return value
Iterator to the first element in the range [first, last)
that is equal to an element from the range [s_first; s_last)
. If no such element is found, last
is returned.
Complexity
Does at most (S*N)
comparisons where S = distance(s_first, s_last) and N = distance(first, 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 InputIt, class ForwardIt> InputIt find_first_of(InputIt first, InputIt last, ForwardIt s_first, ForwardIt s_last) { for (; first != last; ++first) { for (ForwardIt it = s_first; it != s_last; ++it) { if (*first == *it) { return first; } } } return last; } |
Second version |
template<class InputIt, class ForwardIt, class BinaryPredicate> InputIt find_first_of(InputIt first, InputIt last, ForwardIt s_first, ForwardIt s_last, BinaryPredicate p) { for (; first != last; ++first) { for (ForwardIt it = s_first; it != s_last; ++it) { if (p(*first, *it)) { return first; } } } return last; } |
Example
The following code searches for any of specified integers in a vector of integers:
#include <algorithm> #include <iostream> #include <vector> int main() { std::vector<int> v{0, 2, 3, 25, 5}; std::vector<int> t{3, 19, 10, 2}; auto result = std::find_first_of(v.begin(), v.end(), t.begin(), t.end()); if (result == v.end()) { std::cout << "no elements of v were equal to 3, 19, 10 or 2\n"; } else { std::cout << "found a match at " << std::distance(v.begin(), result) << "\n"; } }
Output:
found a match at 1
See also
(C++11) |
finds the first element satisfying specific criteria (function template) |