// Copyright (c) 2018-2022, The Monero Project
//
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without modification, are
// permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this list of
// conditions and the following disclaimer.
//
// 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
// materials provided with the distribution.
//
// 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.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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// Parts of this file are originally copyright (c) 2012-2013 The Cryptonote developers
#pragma once
#include <iostream>
#include <vector>
#include <stdexcept>
namespace tools {
uint64_t combinations_count(uint32_t k, uint32_t n);
template<typename T>
class Combinator {
public:
Combinator(const std::vector<T>& v) : origin(v) { }
std::vector<std::vector<T>> combine(size_t k);
private:
void doCombine(size_t from, size_t k);
std::vector<T> origin;
std::vector<std::vector<T>> combinations;
std::vector<size_t> current;
};
template<typename T>
std::vector<std::vector<T>> Combinator<T>::combine(size_t k)
{
if (k > origin.size())
{
throw std::runtime_error("k must be smaller than elements number");
}
if (k == 0)
{
throw std::runtime_error("k must be greater than zero");
}
combinations.clear();
doCombine(0, k);
return combinations;
}
template<typename T>
void Combinator<T>::doCombine(size_t from, size_t k)
{
current.push_back(0);
for (size_t i = from; i <= origin.size() - k; ++i)
{
current.back() = i;
if (k > 1) {
doCombine(i + 1, k - 1);
} else {
std::vector<T> comb;
for (auto ind: current) {
comb.push_back(origin[ind]);
}
combinations.push_back(comb);
}
}
current.pop_back();
}
} //namespace tools
