Varianti

    std::find, std::find_if, std::find_if_not

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    C++
     
    Algoritmo libreria
    Funzioni
    Original:
    Functions
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    Non modifica le operazioni di sequenza
    Original:
    Non-modifying sequence operations
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    Modifica delle operazioni di sequenza
    Original:
    Modifying sequence operations
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    Partizionamento operazioni
    Original:
    Partitioning operations
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    Ordinamento delle operazioni (su intervalli ordinati)
    Original:
    Sorting operations (on sorted ranges)
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    Binarie (le operazioni di ricerca sui campi ordinati)
    Original:
    Binary search operations (on sorted ranges)
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    Impostare le operazioni (su intervalli ordinati)
    Original:
    Set operations (on sorted ranges)
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    Heap operazioni
    Original:
    Heap operations
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    Minimo / massimo le operazioni
    Original:
    Minimum/maximum operations
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    Operazioni numeriche
    Original:
    Numeric operations
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    Libreria C
    Original:
    C library
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    <tbody> </tbody>
    Elemento definito nell'header <algorithm>
    template< class InputIt, class T > InputIt find( InputIt first, InputIt last, const T& value );
    		 (1)
    template< class InputIt, class UnaryPredicate > InputIt find_if( InputIt first, InputIt last, UnaryPredicate p );
    		 (2)
    template< class InputIt, class UnaryPredicate > InputIt find_if_not( InputIt first, InputIt last, UnaryPredicate q );
    		 (3) (dal C++11)
    Queste funzioni trovare il primo elemento nella [first, last) gamma che soddisfa criteri specifici:
    Original:
    These functions find the first element in the range [first, last) that satisfies specific criteria:
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    1. find ricerche di un elemento pari a value
    Original:
    1. find searches for an element equal to value
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    2. find_if cerca un elemento per il quale predicato p ritorna true
    Original:
    2. find_if searches for an element for which predicate p returns true
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    3. find_if_not cerca elemento per il quale predicato q ritorna false
    Original:
    3. find_if_not searches for element for which predicate q returns false
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    Parametri

    first, last -
    la gamma di elementi da esaminare
    Original:
    the range of elements to examine
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    value -
    valore per confrontare gli elementi
    Original:
    value to compare the elements to
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    p - unary predicate which returns ​true
    per l'elemento richiesto
    Original:
    for the required element
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    .

    The signature of the predicate function should be equivalent to the following:

    bool pred(const Type &a);

    The signature does not need to have const &, but the function must not modify the objects passed to it.
    The type Type must be such that an object of type InputIt can be dereferenced and then implicitly converted to Type. ​

    q - unary predicate which returns ​false
    per l'elemento richiesto
    Original:
    for the required element
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    .

    The signature of the predicate function should be equivalent to the following:

    bool pred(const Type &a);

    The signature does not need to have const &, but the function must not modify the objects passed to it.
    The type Type must be such that an object of type InputIt can be dereferenced and then implicitly converted to Type. ​

    Type requirements
    -
    InputIt must meet the requirements of InputIterator.

    Valore di ritorno

    Iteratore al primo elemento che soddisfa la condizione o last se tale elemento non viene trovato.
    Original:
    Iterator to the first element satisfying the condition or last if no such element is found.
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    Complessità

    Al massimo last - first applicazioni del predicato
    Original:
    At most last - first applications of the predicate
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    Possibile implementazione

    First version 
    template<class InputIt, class T>
InputIt find(InputIt first, InputIt last, const T& value)
{
    for (; first != last; ++first) {
        if (*first == value) {
            return first;
        }
    }
    return last;
}
    Second version 
    template<class InputIt, class UnaryPredicate>
InputIt find_if(InputIt first, InputIt last, UnaryPredicate p)
{
    for (; first != last; ++first) {
        if (p(*first)) {
            return first;
        }
    }
    return last;
}
    Third version 
    template<class InputIt, class UnaryPredicate>
InputIt find_if_not(InputIt first, InputIt last, UnaryPredicate q)
{
    for (; first != last; ++first) {
        if (!q(*first)) {
            return first;
        }
    }
    return last;
}
    Se non si dispone di C + +11, l'equivalente di std::find_if_not è quello di utilizzare std::find_if con il predicato negato.
    Original:
    If you do not have C++11, an equivalent to std::find_if_not is to use std::find_if with the negated predicate.
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    template<class InputIt, class UnaryPredicate>
InputIt find_if_not(InputIt first, InputIt last, UnaryPredicate q)
{
    return std::find_if(first, last, std::not1(q));
}

    Esempio

    Nell'esempio seguente vengono individuati un numero intero in un vettore di interi .
    Original:
    The following example finds an integer in a vector of integers.
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    #include <iostream>
#include <algorithm>
#include <vector>

int main()
{
    int n1 = 3;
    int n2 = 5;
 
    std::vector<int> v{0, 1, 2, 3, 4};
 
    auto result1 = std::find(v.begin(), v.end(), n1);
    auto result2 = std::find(v.begin(), v.end(), n2);
 
    if (result1 != v.end()) {
        std::cout << "v contains: " << n1 << '\n';
    } else {
        std::cout << "v does not contain: " << n1 << '\n';
    }

    if (result2 != v.end()) {
        std::cout << "v contains: " << n2 << '\n';
    } else {
        std::cout << "v does not contain: " << n2 << '\n';
    }
}

    Output: 

    v contains: 3
v does not contain: 5

    Vedi anche
    trova due identici (o qualche altra relazione) elementi adiacenti l'uno all'altro
    Original:
    finds two identical (or some other relationship) items adjacent to each other
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    (funzione di modello) [modifica]
    trova l'ultima sequenza di elementi di un certo intervallo
    Original:
    finds the last sequence of elements in a certain range
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    (funzione di modello) [modifica]
    		searches for any one of a set of elements
    (funzione di modello) [modifica]
    trova la prima posizione in cui due intervalli diversi
    Original:
    finds the first position where two ranges differ
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    (funzione di modello) [modifica]
    		searches for a range of elements
    (funzione di modello) [modifica]