组合和排列在C ++

问题描述

C ++中最广泛使用的现有库提供了n个元素中k个元素的所有组合和排列？

What's the most widely used existing library in C++ to give all the combination and permutation of k elements out of n elements?

我不是要求算法，现有的库或方法。

I am not asking the algorithm but the existing library or methods.

感谢。

推荐答案

组合： Mark Nelson关于同一主题的文章，我们有next_combination 排列：从STL我们有std :: next_permutation

Combinations: from Mark Nelson's article on the same topic we have next_combination http://marknelson.us/2002/03/01/next-permutation Permutations: from STL we have std::next_permutation

   template <typename Iterator>
   inline bool next_combination(const Iterator first, Iterator k, const Iterator last)
   {
      if ((first == last) || (first == k) || (last == k))
         return false;
      Iterator itr1 = first;
      Iterator itr2 = last;
      ++itr1;
      if (last == itr1)
         return false;
      itr1 = last;
      --itr1;
      itr1 = k;
      --itr2;
      while (first != itr1)
      {
         if (*--itr1 < *itr2)
         {
            Iterator j = k;
            while (!(*itr1 < *j)) ++j;
            std::iter_swap(itr1,j);
            ++itr1;
            ++j;
            itr2 = k;
            std::rotate(itr1,j,last);
            while (last != j)
            {
               ++j;
               ++itr2;
            }
            std::rotate(k,itr2,last);
            return true;
         }
      }
      std::rotate(first,k,last);
      return false;
   }

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