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std::nth_element

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< cpp‎ | algorithm

 
 
アルゴリズムライブラリ
機能します
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Functions
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シーケンス動作を非改変
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Non-modifying sequence operations
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シーケンス動作を変更する
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Modifying sequence operations
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操作を仕切る
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Partitioning operations
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(ソートされた範囲で)ソート操作
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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 RandomIt >
void nth_element( RandomIt first, RandomIt nth, RandomIt last );
(1)
template< class RandomIt, class Compare >
void nth_element( RandomIt first, RandomIt nth, RandomIt last, Compare comp );
(2)
部分的にソートされるように昇順で範囲[first, last)範囲内のすべての要素[first, nth)アール範囲[nth, last)に比べて少ない。最初のバージョンは、要素を比較するoperator<使用して、2番目のバージョンは、指定された比較関数compを使用しています。 nth位置に配置要素は、正確に範囲が完全にソートされていた場合、この位置に現れることになる要素です.
Original:
Partially sorts the range [first, last) in ascending order so that all elements in the range [first, nth) are less than those in the range [nth, last). The first version uses operator< to compare the elements, the second version uses the given comparison function comp. The element placed in the nth position is exactly the element that would occur in this position if the range was fully sorted.
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目次

[編集] パラメータ

first, last -
範囲のソートを定義するランダムアクセス反復子
Original:
random access iterators defining the range sort
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nth -
ソート·パーティション·ポイントを定義するランダムアクセス反復子を返します
Original:
random access iterator defining the sort partition point
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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 an object of type RandomIt can be dereferenced and then implicitly converted to both of them. ​

Type requirements
-
RandomIt must meet the requirements of ValueSwappable and RandomAccessIterator.
-
The type of dereferenced RandomIt must meet the requirements of MoveAssignable and MoveConstructible.

[編集] 値を返します

(なし)
Original:
(none)
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[編集] 複雑

平均でstd::distance(first, last)におけるリニア.
Original:
Linear in std::distance(first, last) on average.
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[編集]

#include <iostream>
#include <vector>
#include <algorithm>
#include <functional>
 
int main()
{
    std::vector<int> v{5, 6, 4, 3, 2, 6, 7, 9, 3};
 
    std::nth_element(v.begin(), v.begin() + v.size()/2, v.end());
    std::cout << "The median is " << v[v.size()/2] << '\n';
 
    std::nth_element(v.begin(), v.begin()+1, v.end(), std::greater<int>());
    std::cout << "The second largest element is " << v[1] << '\n';
}

Output:

The median is 5
The second largest element is 7

[編集] も参照してください

コピーと部分的にソートする要素の範囲
Original:
copies and partially sorts a range of elements
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(関数テンプレート) [edit]
ソートされた範囲の要素を等しい要素間の順序を維持しながら
Original:
sorts a range of elements while preserving order between equal elements
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(関数テンプレート) [edit]
昇順にソートする範囲
Original:
sorts a range into ascending order
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(関数テンプレート) [edit]