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std::set_difference

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< cpp‎ | algorithm

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C++
 
Algoritmo libreria
Funzioni
Original:
Functions
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Non modifica le operazioni di sequenza
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Non-modifying sequence operations
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Modifica delle operazioni di sequenza
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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)
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Set operations (on sorted ranges)
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Heap operazioni
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Heap operations
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Minimo / massimo le operazioni
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Minimum/maximum operations
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Operazioni numeriche
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Numeric operations
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Libreria C
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C library
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Elemento definito nell'header <algorithm>
template< class InputIt1, class InputIt2, class OutputIt >

OutputIt set_difference( InputIt1 first1, InputIt1 last1,
                         InputIt2 first2, InputIt2 last2,

                         OutputIt d_first );
 (1)
template< class InputIt1, class InputIt2,

          class OutputIt, class Compare >
OutputIt set_difference( InputIt1 first1, InputIt1 last1,
                         InputIt2 first2, InputIt2 last2,

                         OutputIt d_first, Compare comp );
 (2)
Copia gli elementi della gamma [first1, last1) ordinato che non si trovano nel campo di [first2, last2) ordinato all'inizio gamma a d_first.
Original:
Copies the elements from the sorted range [first1, last1) which are not found in the sorted range [first2, last2) to the range beginning at d_first.
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Il campo risultante è anche ordinato. La prima versione si aspetta che sia l'ingresso che varia da ordinare con operator<, la seconda versione si aspetta che essere ordinati con il confronto comp data funzione. Elementi equivalenti sono trattati singolarmente, cioè se qualche elemento è trovato m volte in [first1, last1) e n volte in [first2, last2), verrà copiato d_first esattamente std::max(m-n, 0) volte. L'intervallo risultante non possono sovrapporsi uno dei campi di ingresso.
Original:
The resulting range is also sorted. The first version expects both input ranges to be sorted with operator<, the second version expects them to be sorted with the given comparison function comp. Equivalent elements are treated individually, that is, if some element is found m times in [first1, last1) and n times in [first2, last2), it will be copied to d_first exactly std::max(m-n, 0) times. The resulting range cannot overlap with either of the input ranges.
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Indice

[modifica] Parametri

first1, last1 -
la gamma di elementi da esaminare
Original:
the range of elements to examine
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first2, last2 -
la gamma di elementi da cercare
Original:
the range of elements to search for
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comp - comparison function which returns ​true if the first argument is less than the second.

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

 bool cmp(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 InputIt1 and InputIt2 can be dereferenced and then implicitly converted to Type1 and Type2 respectively. ​

Type requirements
-
InputIt1 must meet the requirements of InputIterator.
-
InputIt2 must meet the requirements of InputIterator.
-
OutputIt must meet the requirements of OutputIterator.

[modifica] Valore di ritorno

Iterator oltre la fine della gamma costruito.
Original:
Iterator past the end of the constructed range.
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[modifica] Complessità

A confronto la maggior parte 2·(N1+N2-1), dove N1 = std::distance(first1, last1) e N2 = std::distance(first2, last2).
Original:
At most 2·(N1+N2-1) comparisons, where N1 = std::distance(first1, last1) and N2 = std::distance(first2, last2).
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[modifica] Possibile implementazione

First version 
template<class InputIt1, class InputIt2, class OutputIt>
OutputIt set_difference(InputIt1 first1, InputIt1 last1,
                        InputIt2 first2, InputIt2 last2,
                        OutputIt d_first)
{
    while (first1 != last1) {
        if (first2 == last2) return std::copy(first1, last1, d_first);
 
        if (*first1 < *first2) {
            *d_first++ = *first1++;
        } else {
            if (! (*first2 < *first1)) {
                ++first1;
            }
            ++first2;
        }
    }
    return d_first;
}
Second version 
template<class InputIt1, class InputIt2,
         class OutputIt, class Compare>
OutputIt set_difference( InputIt1 first1, InputIt1 last1,
                         InputIt2 first2, InputIt2 last2,
                         OutputIt d_first, Compare comp)
{
    while (first1 != last1) {
        if (first2 == last2) return std::copy(first1, last1, d_first);
 
        if (comp(*first1, *first2)) {
            *d_first++ = *first1++;
        } else {
            if (!comp(*first2, *first1)) {
                ++first1;
            }
            ++first2;
        }
    }
    return d_first;
}

[modifica] Esempio

#include <iostream>
#include <algorithm>
#include <vector>
#include <iterator>
 
int main() {
    std::vector<int> v1 {1, 2, 5, 5, 5, 9};
    std::vector<int> v2 {2, 5, 7};
    std::vector<int> diff;
 
    std::set_difference(v1.begin(), v1.end(), v2.begin(), v2.end(), 
                        std::inserter(diff, diff.begin()));
 
    for (auto i : v1) std::cout << i << ' ';
    std::cout << "minus ";
    for (auto i : v2) std::cout << i << ' ';
    std::cout << "is: ";
 
    for (auto i : diff) std::cout << i << ' ';
    std::cout << '\n';
}

Output: 

1 2 5 5 5 9 minus 2 5 7 is: 1 5 5 9

[modifica] Vedi anche
restituisce true se un insieme è un sottoinsieme di un altro
Original:
returns true if one set is a subset of another
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(funzione di modello) [modifica]
calcola la differenza simmetrica tra due insiemi
Original:
computes the symmetric difference between two sets
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(funzione di modello) [modifica]
Estratto da "https://it.cppreference.com/mwiki/index.php?title=cpp/algorithm/set_difference&oldid=24988"