// Copyright (c) 2018-2022, The Monero Project

//
// All rights reserved.
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// permitted provided that the following conditions are met:
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// 1. Redistributions of source code must retain the above copyright notice, this list of
//    conditions and the following disclaimer.
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// 2. Redistributions in binary form must reproduce the above copyright notice, this list
//    of conditions and the following disclaimer in the documentation and/or other
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// 3. Neither the name of the copyright holder nor the names of its contributors may be
//    used to endorse or promote products derived from this software without specific
//    prior written permission.
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
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// Parts of this file are originally copyright (c) 2012-2013 The Cryptonote developers

#include "combinator.h"

namespace tools {

uint64_t combinations_count(uint32_t k, uint32_t n)
{
  if (k > n) {
    throw std::runtime_error("k must not be greater than n");
  }

  uint64_t c = 1;
  for (uint64_t i = 1; i <= k; ++i) {
    c *= n--;
    c /= i;
  }

  return c;
}

}