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std::lexicographical_compare

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< cpp‎ | algorithm

 
 
Algoritmo libreria
Funzioni
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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
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Partitioning operations
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Ordinamento delle operazioni (su intervalli ordinati)
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Sorting operations (on sorted ranges)
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Binarie (le operazioni di ricerca sui campi ordinati)
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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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lexicographical_compare
is_permutation(C++11)
next_permutation
prev_permutation
Operazioni numeriche
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Numeric operations
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Libreria C
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C library
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Defined in header <algorithm>
template< class InputIt1, class InputIt2 >

bool lexicographical_compare( InputIt1 first1, InputIt1 last1,

                              InputIt2 first2, InputIt2 last2 );
(1)
template< class InputIt1, class InputIt2, class Compare >

bool lexicographical_compare( InputIt1 first1, InputIt1 last1,
                              InputIt2 first2, InputIt2 last2,

                              Compare comp );
(2)
Controlla se il primo intervallo è [first1, last1) lexicographically' inferiore al [first2, last2) secondo intervallo. La prima versione utilizza operator< di confrontare gli elementi, la seconda versione utilizza la funzione di confronto dato comp.
Original:
Checks if the first range [first1, last1) is lexicographically less than the second range [first2, last2). The first version uses operator< to compare the elements, the second version uses the given comparison function comp.
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Confronto lessicografico è un'operazione con le seguenti proprietà:
Original:
Lexicographical comparison is a operation with the following properties:
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  • Due campi sono confrontati elemento per elemento.
    Original:
    Two ranges are compared element by element.
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  • L'elemento mismatching prima definisce quale intervallo è lexicographically meno o' superiore rispetto agli altri.
    Original:
    The first mismatching element defines which range is lexicographically less or greater than the other.
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  • Se un intervallo è un prefisso di un altro, la gamma più breve è lexicographically' di meno rispetto agli altri.
    Original:
    If one range is a prefix of another, the shorter range is lexicographically less than the other.
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  • Se due serie hanno elementi equivalenti e sono della stessa lunghezza, gli intervalli sono uguali lessicograficamente'.
    Original:
    If two ranges have equivalent elements and are of the same length, then the ranges are lexicographically equal.
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  • Un campo a vuoto è lexicographically' meno di qualsiasi non vuota gamma.
    Original:
    An empty range is lexicographically less than any non-empty range.
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  • Due campi sono vuoti lessicografico' uguali.
    Original:
    Two empty ranges are lexicographically equal.
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Indice

[modifica] Parametri

first1, last1 -
la prima gamma di elementi da esaminare
Original:
the first range of elements to examine
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first2, last2 -
il secondo intervallo di elementi da esaminare
Original:
the second range of elements to examine
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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, InputIt2 must meet the requirements of InputIterator.

[modifica] Valore di ritorno

true se il primo intervallo è lexicographically meno della seconda.
Original:
true if the first range is lexicographically less than the second.
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[modifica] Complessità

Alla maggior parte delle applicazioni di 2·min(N1, N2) l'operazione di confronto, dove N1 = std::distance(first1, last1) e N2 = std::distance(first2, last2).
Original:
At most 2·min(N1, N2) applications of the comparison operation, 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>
bool lexicographical_compare(InputIt1 first1, InputIt1 last1,
                             InputIt2 first2, InputIt2 last2)
{
    for ( ; (first1 != last1) && (first2 != last2); first1++, first2++ ) {
        if (*first1 < *first2) return true;
        if (*first2 < *first1) return false;
    }
    return (first1 == last1) && (first2 != last2);
}
Second version
template<class InputIt1, class InputIt2, class Compare>
bool lexicographical_compare(InputIt1 first1, InputIt1 last1,
                             InputIt2 first2, InputIt2 last2,
                             Compare comp)
{
    for ( ; (first1 != last1) && (first2 != last2); first1++, first2++ ) {
        if (comp(*first1, *first2)) return true;
        if (comp(*first2, *first1)) return false;
    }
    return (first1 == last1) && (first2 != last2);
}

[modifica] Esempio

#include <algorithm>
#include <iostream>
#include <vector>
#include <cstdlib>
#include <ctime>
 
int main()
{
    std::vector<char> v1 {'a', 'b', 'c', 'd'};
    std::vector<char> v2 {'a', 'b', 'c', 'd'};
 
    std::srand(std::time(0));
    while (!std::lexicographical_compare(v1.begin(), v1.end(),
                                         v2.begin(), v2.end())) {
        for (auto c : v1) std::cout << c << ' ';
        std::cout << ">= ";
        for (auto c : v2) std::cout << c << ' ';
        std::cout << '\n';
 
        std::random_shuffle(v1.begin(), v1.end());
        std::random_shuffle(v2.begin(), v2.end());
    }
 
    for (auto c : v1) std::cout << c << ' ';
    std::cout << "< ";
    for (auto c : v2) std::cout << c << ' ';
    std::cout << '\n';
}

Possible output:

a b c d >= a b c d 
d a b c >= c b d a 
b d a c >= a d c b 
a c d b < c d a b