std::find_first_of - cppreference.com

Da cppreference.com.

Questa pagina è stata tradotta in modo automatico dalla versione in ineglese della wiki usando Google Translate.

La traduzione potrebbe contenere errori e termini strani. Muovi il puntatore sopra al testo per vedere la versione originale. Puoi aiutarci a correggere gli gli errori. Per ulteriori istruzioni clicca qui.

Click here for the English version of this page

Elemento definito nell'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)	(fino al c++11) (dal 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)	(fino al c++11) (dal C++11)

Cerca nella [first, last) gamma per ogni elemento della [s_first, s_last) gamma. La prima versione utilizza operator== di confrontare gli elementi, la seconda versione utilizza il predicato binario dato 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.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Parametri

first, last	-	la gamma di elementi da esaminare Original: the range of elements to examine The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
s_first, s_last	-	la gamma di elementi da cercare Original: the range of elements to search for The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
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`.

Valore di ritorno

Iteratore al primo elemento nella [first, last) gamma che è uguale a un elemento dal [s_first; s_last) gamma. Se tale elemento non viene trovato, viene restituito 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.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Complessità

Fa a confronto la maggior parte (S*N) dove S = distance(s_first, s_last) e N = distance(first, last).

Original:

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

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Possibile implementazione

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; }

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;
}

Esempio

Le ricerche di codice seguenti per uno qualsiasi dei numeri interi specificati in un vettore di interi:

Original:

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

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

#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:

Vedi anche


	trova il primo elemento che soddisfi i criteri specifici Original: finds the first element satisfying specific criteria The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (funzione di modello) [modifica]