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std::merge - cppreference.com

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Definido no cabeçalho

<algorithm>

template< class InputIt1, class InputIt2, class OutputIt > OutputIt merge( InputIt1 first1, InputIt1 last1, InputIt2 first2, InputIt2 last2 OutputIt d_first );

 (1)

template< class InputIt1, class InputIt2, class OutputIt, class Compare> OutputIt merge( InputIt1 first1, InputIt1 last1, InputIt2 first2, InputIt2 last2 OutputIt d_first, Compare comp );

 (2)

Mescla duas faixas classificadas [first1, last1) e [first2, last2) em um intervalo classificado no início d_first. A primeira versão utiliza operator< para comparar os elementos, a segunda versão utiliza o comp dada função de comparação. A ordem relativa dos elementos equivalentes são preservados.

Original:

Merges two sorted ranges [first1, last1) and [first2, last2) into one sorted range beginning at d_first. The first version uses operator< to compare the elements, the second version uses the given comparison function comp. The relative order of equivalent elements is preserved.

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Parâmetros

first1, last1 -

a primeira gama de elementos para a fusão

Original:

the first range of elements to merge

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first2, last2 -

a segunda faixa de elementos de fusões

Original:

the second range of elements to merge

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d_first -

o início do intervalo de destino

Original:

the beginning of the destination range

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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.

Valor de retorno

Um iterador elemento de saída para além do último elemento copiado.

Original:

An output iterator to element past the last element copied.

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Complexidade

Na maioria das comparações dos std::distance(first1, last1) + std::distance(first2, last2) + 1.

Original:

At most std::distance(first1, last1) + std::distance(first2, last2) + 1 comparisons.

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Possível implementação

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

Exemplo

#include <iostream>
#include <iterator>
#include <cstdlib>
#include <algorithm>
#include <vector>
 
int main() 
{
    const std::size_t items = 10;
 
    std::vector<int> v1, v2, dst;
 
    // fill the vectors
    for (std::size_t idx = 0; idx < items; ++idx) {
        v1.push_back(std::rand()%items);
        v2.push_back(std::rand()%items);
    }
 
    // sort
    std::sort(v1.begin(), v1.end());
    std::sort(v2.begin(), v2.end());

    // output v1
    std::cout << "v1 : ";
    std::copy(v1.begin(), v1.end(),
              std::ostream_iterator<int>(std::cout, " "));
    std::cout << '\n';
   
    // output v2
    std::cout << "v2 : ";
    std::copy(v2.begin(), v2.end(),
              std::ostream_iterator<int>(std::cout, " "));
    std::cout << '\n';
 
    // merge
    std::merge(v1.begin(), v1.end(),
               v2.begin(), v2.end(),
               std::back_inserter(dst));
 
    // output
    std::cout << "dst: ";
    std::copy(dst.begin(), dst.end(),
             std::ostream_iterator<int>(std::cout, " "));
    std::cout << '\n';
}

Saída: 

v1 : 0 0 2 2 3 3 3 6 7 9 
v2 : 1 2 5 5 6 6 6 6 7 9 
dst: 0 0 1 2 2 2 3 3 3 5 5 6 6 6 6 6 7 7 9 9

Veja também

funde duas faixas encomendadas no local

Original:

merges two ordered ranges in-place

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(modelo de função) [edit]

tipo um intervalo em ordem crescente

Original:

sorts a range into ascending order

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(modelo de função) [edit]

Classifica um intervalo de elementos preservando ordem entre elementos iguais

Original:

sorts a range of elements while preserving order between equal elements

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(modelo de função) [edit]