std::find_first_of
From Cppreference
| Defined in header <algorithm>
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| template< class ForwardIterator1, class ForwardIterator2 >
ForwardIterator1 find_first_of( ForwardIterator1 first, ForwardIterator1 last, |
(1) | |
| template< class ForwardIterator1, class ForwardIterator2, class BinaryPredicate >
ForwardIterator1 find_first_of( ForwardIterator1 first, ForwardIterator1 last, |
(2) | |
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:
The signature does not need to have const &, but the function must not modify the objects passed to it. |
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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] Equivalent function
| First version |
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template<class ForwardIterator1, class ForwardIterator2> ForwardIterator1 find_first_of(ForwardIterator1 first, ForwardIterator1 last, ForwardIterator2 s_first, ForwardIterator2 s_last) { for (; first != last; ++first) { for (ForwardIterator2 it = sfirst; it != s_last; ++it) { if (*first == *it) { return first; } } } return last; } |
| Second version |
template<class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> ForwardIterator1 find_first_of(ForwardIterator1 first, ForwardIterator1 last, ForwardIterator2 s_first, ForwardIterator2 s_last, BinaryPredicate p) { for (; first != last; ++first) { for (ForwardIterator2 it = sfirst; 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, 1, 2, 3, 4, 5}; std::vector<int> t{3, 19, 2}; auto result = std::find_first_of(v.begin(), v.end(), t.begin(), t.end()); if (*result == v.end()) { std::cout << "any of {3, 19, 2} not found"; } else { std::cout << "found a match at " << std::distance(v.begin(), result) << "\n"; } }
Output:
found a match at 2
[edit] See also
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finds the first element satisfying specific criteria (function template) |
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