60 lines
1.7 KiB
C++
60 lines
1.7 KiB
C++
#pragma once
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#include <boost/container/flat_set.hpp>
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#include <vector>
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// Using boost flat set was faster than std::set.
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template <typename Field, typename Cluster>
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auto make_empty(Field field, Cluster const & c){
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for(auto&& p : c){
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field.get(p) = 0;
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}
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field.collapse();
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return field;
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}
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namespace detail {
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template <typename Field, typename Rules>
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void cluster_expand(Field const & field, Rules const & rules, typename Field::Position const & p, boost::container::flat_set<typename Field::Position>& ret){
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for(auto&& q : field.neighbors(p)){
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if(!rules.same_cluster(field.get(p), field.get(q))) continue;
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if(ret.insert(q).second){
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cluster_expand(field, rules, q, ret);
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}
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}
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}
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}
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template <typename Field, typename Rules>
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auto cluster_at(Field const & field, Rules const & rules, typename Field::Position const & p){
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boost::container::flat_set<typename Field::Position> ret;
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ret.reserve(10); // speed improvement of 20%
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ret.insert(p);
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detail::cluster_expand(field, rules, p, ret);
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return ret;
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}
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template <typename Grid, typename Rules>
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auto all_clusters(Grid const & grid, Rules const & rules){
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std::vector<decltype(cluster_at(grid, rules, std::declval<typename Grid::Position>()))> ret;
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ret.reserve(10);
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auto partition = make_empty(grid, grid.all_positions());
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auto current_p = 1;
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for(auto&& p : partition.all_positions()){
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// ignore if it already belongs to a cluster or is empty
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if(!partition.empty(p) || grid.empty(p)) continue;
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auto cluster = cluster_at(grid, rules, p);
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for(auto&& q : cluster){
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partition.get(q) = current_p;
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}
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current_p++;
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if(cluster.size() >= rules.min_cluster_size()) ret.push_back(std::move(cluster));
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}
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return ret;
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}
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