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std::partition

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< cpp‎ | algorithm

 
 
アルゴリズムライブラリ
機能します
Original:
Functions
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シーケンス動作を非改変
Original:
Non-modifying sequence operations
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シーケンス動作を変更する
Original:
Modifying sequence operations
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操作を仕切る
Original:
Partitioning operations
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is_partitioned(C++11)
partition
partition_copy(C++11)
(ソートされた範囲で)ソート操作
Original:
Sorting operations (on sorted ranges)
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バイナリ検索操作(ソート範囲で)
Original:
Binary search operations (on sorted ranges)
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(ソートされた範囲で)操作を設定します
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Set operations (on sorted ranges)
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ヒープ操作
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Heap operations
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最小値/最大値操作
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Minimum/maximum operations
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数値演算
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Numeric operations
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Cライブラリ
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C library
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Defined in header <algorithm>
template< class BidirIt, class UnaryPredicate >

BidirectionalIterator partition( BidirIt first, BidirIt last,
                                 UnaryPredicate p );
template< class ForwardIt, class UnaryPredicate >
ForwardIt partition( ForwardIt first, ForwardIt last,

                     UnaryPredicate p );
(C + + 11時まで)

(C + + 11以来)
並べ替えるには、そのような方法でレンジ[first, last)の要素、そのすべての要素どちらの述語p戻りtrue要素に先行するための述語p戻りfalse。要素の相対的な順序は保持されません.
Original:
Reorders the elements in the range [first, last) in such a way that all elements for which the predicate p returns true precede the elements for which predicate p returns false. Relative order of the elements is not preserved.
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目次

[編集] パラメータ

first, last -
順序を変更する要素の範囲
Original:
the range of elements to reorder
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p - unary predicate which returns ​true
要素は他の要素の前に発注する必要があります
Original:
if the element should be ordered before other elements
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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 ForwardIt can be dereferenced and then implicitly converted to Type. ​

Type requirements
-
BidirIt must meet the requirements of BidirectionalIterator.
-
ForwardIt must meet the requirements of ValueSwappable and ForwardIterator. However, the operation is more efficient if ForwardIt also satisfies the requirements of BidirectionalIterator

[編集] 値を返します

第二のグループの最初の要素へのイテレータ.
Original:
Iterator to the first element of the second group.
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[編集] 複雑

述語の正確last-firstアプリケーションとせいぜいlast-firstスワップ。 ForwardItが最もBidirectionalIteratorスワップで(last-first)/2の要件を満たしている場合に行われ.
Original:
Exactly last-first applications of the predicate and at most last-first swaps. If ForwardIt meets the requirements of BidirectionalIterator at most (last-first)/2 swaps are done.
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[編集] 可能な実装

template<class BidirIt, class UnaryPredicate>
BidirIt partition(BidirIt first, BidirIt last, UnaryPredicate p)
{
    while (1) {
        while ((first != last) && p(*first)) {
            ++first;
        }
        if (first == last--) break;
        while ((first != last) && !p(*last)) {
            --last;
        }
        if (first == last) break;
        std::swap(*first++, *last);
    }
    return first;
}

[編集]

#include <algorithm>
#include <functional>
#include <iostream>
#include <iterator>
#include <vector>
 
bool is_even(int i) { return i % 2 == 0; }
 
int main()
{
    std::vector<int> v;
    for (int i = 0; i < 10; ++i) v.push_back(i);
 
    std::cout << "Original vector:\n    ";
    std::copy(v.begin(), v.end(), std::ostream_iterator<int>(std::cout, " "));
 
    // Partition the vector
    std::vector<int>::iterator p =
        std::partition(v.begin(), v.end(), std::ptr_fun(is_even));
 
    std::cout << "\nPartitioned vector:\n    ";
    std::copy(v.begin(), v.end(), std::ostream_iterator<int>(std::cout, " "));
    std::cout << "\nBefore partition:\n    ";
    std::copy(v.begin(), p,       std::ostream_iterator<int>(std::cout, " "));
    std::cout << "\nAfter partition:\n    ";
    std::copy(p,         v.end(), std::ostream_iterator<int>(std::cout, " "));
}

Possible output:

Original vector:
    0 1 2 3 4 5 6 7 8 9 
Partitioned vector:
    0 8 2 6 4 5 3 7 1 9 
Before partition:
    0 8 2 6 4 
After partition:
    5 3 7 1 9

[編集] も参照してください

範囲が指定された述語によって仕切られているかどうかを判断します
Original:
determines if the range is partitioned by the given predicate
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(関数テンプレート) [edit]
それらの相対的な順序を維持しながら、二つのグループに要素を分割します
Original:
divides elements into two groups while preserving their relative order
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(関数テンプレート) [edit]