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std::find_first_of – cppreference.com

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definiert in Header

<algorithm>

template< class ForwardIt1, class ForwardIt2 > ForwardIt1 find_first_of( ForwardIt1 first, ForwardIt1 last, ForwardIt2 s_first, ForwardIt2 s_last ); template< class InputIt, class ForwardIt > InputIt find_first_of( InputIt first, InputIt last, ForwardIt s_first, ForwardIt s_last );

 (1) (bis C + +11)

(seit C++11)

template< class ForwardIt1, class ForwardIt2, class BinaryPredicate > ForwardIt1 find_first_of( ForwardIt1 first, ForwardIt1 last, ForwardIt2 s_first, ForwardIt2 s_last, BinaryPredicate p ); template< class InputIt, class ForwardIt, class BinaryPredicate > InputIt find_first_of( InputIt first, InputIt last, ForwardIt s_first, ForwardIt s_last, BinaryPredicate p );

 (2) (bis C + +11)

(seit C++11)

Durchsucht den Bereich [first, last) für jedes der Elemente im Bereich [s_first, s_last). Die erste Version verwendet operator== um die Elemente zu vergleichen, verwendet die zweite Version des gegebenen binären Prädikats p .

Original:

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.

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Parameter

first, last -

das Spektrum der Elemente zu untersuchen

Original:

the range of elements to examine

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s_first, s_last -

der Bereich der Elemente für

Original:

the range of elements to search for

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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.
The types Type1 and Type2 must be such that objects of types ForwardIt1 and ForwardIt2 can be dereferenced and then implicitly converted to Type1 and Type2 respectively.

​

Type requirements
-InputIt must meet the requirements of InputIterator.
-ForwardIt1 must meet the requirements of ForwardIterator.
-ForwardIt2 must meet the requirements of ForwardIterator.

Rückgabewert

Iterator zum ersten Element in dem Bereich [first, last), die gleich einem Element, ausgewählt aus dem Bereich [s_first; s_last) ist. Wenn ein solches Element gefunden wird, wird zurückgegeben last .

Original:

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.

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Komplexität

Ist in den meisten (S*N) Vergleiche, wo S = distance(s_first, s_last) und N = distance(first, last) .

Original:

Does at most (S*N) comparisons where S = distance(s_first, s_last) and N = distance(first, last).

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Mögliche Implementierung

First version 
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;
}

Beispiel

Die folgenden Code sucht nach einem der genannten Zahlen in einen Vektor von ganzen Zahlen:

Original:

The following code searches for any of specified integers in a vector of integers:

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#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:

Siehe auch