ah-comb-generators.H

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/*
                          Aleph_w
 
  Data structures & Algorithms
  https://github.com/lrleon/Aleph-w
 
  This file is part of Aleph-w library
 
  Copyright (c) 2002-2026 Leandro Rabindranath Leon
 
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  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
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*/
 
#ifndef AH_COMB_GENERATORS_H
#define AH_COMB_GENERATORS_H
 
#include <ah-comb.H>
#include <ah-generator.H>
#include <tpl_array.H>
#include <tpl_sort_utils.H>
 
namespace Aleph
{
 
template <typename T, class Compare = Aleph::less<T>>
Aleph::Generator<Array<T>> lazy_permutations(Array<T> a, Compare cmp = Compare())
{
  timsort(a, cmp);
  co_yield a;
  while (next_permutation(a, cmp, false))
    co_yield a;
}
 
template <typename T>
Aleph::Generator<Array<T>> lazy_combinations(Array<T> a, size_t k)
{
  const size_t n = a.size();
  ah_domain_error_if(k > n) << "lazy_combinations: k=" << k << " cannot exceed n=" << n;
 
  if (k == 0)
    {
      co_yield Array<T>();
      co_return;
    }
 
  Array<size_t> idx(k);
  idx.putn(k);
  for (size_t i = 0; i < k; ++i)
    idx[i] = i;
 
  do
    {
      Array<T> combo(k);
      for (size_t i = 0; i < k; ++i)
        combo.append(a[idx[i]]);
      co_yield combo;
    }
  while (next_combination_indices(idx, n, false));
}
 
} // end namespace Aleph
 
#endif // AH_COMB_GENERATORS_H