66 lines
2.1 KiB
C++
66 lines
2.1 KiB
C++
/*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*
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* Copyright:
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* 2018, Danny Robson <danny@nerdcruft.net>
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*/
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#pragma once
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#include "../types/traits.hpp"
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#include <iterator>
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#include <functional>
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namespace cruft::search {
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/// Performs a linear search to discover the iterator corresponding to
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/// the value which minimises a function.
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///
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/// Useful as a mechanism to avoid possibly expensive comparison
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/// calculations; eg recomputing path distances when testing a series of
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/// possible routes.
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///
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/// The provided function will be invoked with the supplied argument pack
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/// as the first arguments and the dereferenced iterator as the final
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/// argument.
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///
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/// \tparam ForwardT A forward iterator
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/// \tparam FunctionT An invokable
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/// \param first The first iterator in the range to be searched
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/// \param last The last iterator in the range to be searched
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/// \param func A functional which returns a comparable value
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/// \param args The first arguments passed to `func`
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/// \return A pair of the best score, and the best iterator
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template <
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typename ForwardT,
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typename FunctionT,
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typename ...Args
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>
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auto
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minimises (
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ForwardT first,
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ForwardT last,
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FunctionT &&func,
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Args &&...args
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) {
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using value_type = typename std::iterator_traits<ForwardT>::value_type;
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using score_t = std::invoke_result_t<FunctionT, Args..., value_type>;
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static_assert (::cruft::is_less_than_comparable_v<score_t,score_t>);
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auto best_score = std::invoke (func, args..., *first);
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auto best_item = first;
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for (++first; first != last; ++first) {
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auto this_score = std::invoke (func, args..., *first);
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if (this_score < best_score) {
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best_score = this_score;
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best_item = first;
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}
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}
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return std::pair (std::move (best_score), std::move (best_item));
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}
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} |