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std::prev_permutation

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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)
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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 >
bool prev_permutation( BidirIt first, BidirIt last);
(1)
template< class BidirIt, class Compare >
bool prev_permutation( BidirIt first, BidirIt last, Compare comp);
(2)
辞書的に[first, last)またはoperator<に対して順序付けされているすべての順列の集合から以前順列に範囲compを変換します。返しtrue場合など順列が存在すると、そうでなければ最後の順列に範囲を変換します(std::sort(first, last); std::reverse(first, last);であれば)を返しfalse.
Original:
Transforms the range [first, last) into the previous permutation from the set of all permutations that are lexicographically ordered with respect to operator< or comp. Returns true if such permutation exists, otherwise transforms the range into the last permutation (as if by std::sort(first, last); std::reverse(first, last);) and returns false.
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目次

[編集] パラメータ

first, last -
ランダムな置換をする要素の範囲
Original:
the range of elements to permute
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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 BidirIt can be dereferenced and then implicitly converted to both of them. ​

Type requirements
-
BidirIt must meet the requirements of ValueSwappable and BidirectionalIterator.

[編集] 値を返します

新しい順列が辞書式順序で古いの前true場合。 false第一順列に達していて、範囲は最後の順列にリセットされていた場合..
Original:
true if the new permutation precedes the old in lexicographical order. false if the first permutation was reached and the range was reset to the last permutation.
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[編集] 複雑

最も(last-first)/2スワップで.
Original:
At most (last-first)/2 swaps.
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[編集] 可能な実装

template<class BidirIt>
bool prev_permutation(BidirIt first, BidirIt last)
{
    if (first == last) return false;
    BidirIt i = last;
    if (first == --i) return false;
 
    while (1) {
        BidirIt i1, i2;
 
        i1 = i;
        if (*i1 < *--i) {
            i2 = last;
            while (!(*--i2 < *i))
                ;
            std::iter_swap(i, i2);
            std::reverse(i1, last);
            return true;
        }
        if (i == first) {
            std::reverse(first, last);
            return false;
        }
    }
}

[編集]

次のコードは、文字列を逆の順序で "abc"のすべての6つの順列を出力します
Original:
The following code prints all six permutations of the string "abc" in reverse order
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#include <algorithm>
#include <string>
#include <iostream>
#include <functional>
int main()
{
    std::string s="abc";
    std::sort(s.begin(), s.end(), std::greater<char>());
    do {
        std::cout << s << ' ';
    } while(std::prev_permutation(s.begin(), s.end()));
    std::cout << '\n';
}

Output:

cba cab bca bac acb abc

[編集] も参照してください

determines if a sequence is a permutation of another sequence
(関数テンプレート) [edit]
prev_permutation
generates the next smaller lexicographic permutation of a range of elements
(関数テンプレート) [edit]