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) | |
(2) | ||
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) | |
Searches the range [first, last)
for any of the elements in the range [s_first, s_last)
. The first version uses operator==
to compare the elements, the second version uses the given binary predicate p
.
Contents |
[edit] Parameters
first, last | - | the range of elements to examine |
s_first, s_last | - | the range of elements to search for |
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); 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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ForwardIt1 must meet the requirements of ForwardIterator .
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ForwardIt2 must meet the requirements of ForwardIterator .
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[edit] 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.
[edit] Complexity
Does at most (S*N)
comparisons where S = distance(s_first, s_last) and N = distance(first, last).
[edit] 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; } |
[edit] 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
[edit] See also
(C++11)
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finds the first element satisfying specific criteria (function template) |
(parallelism TS)
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parallelized version of std::find_first_of (function template) |