boost::icl::interval_map重叠并集

boost::icl::interval_map union on overlap

本文关键字：重叠 map icl interval boost      更新时间：2023-10-16

是否可以使interval_map具有以下累积行为：

[1..3]->1 +
[2..4]->2 +
[5..7]->3 +
[6..8]->4
=
[1..4]->{1,2}, [5..8]->{3,4}
+
[3..6]->42
=
[1..8]->{1,2,3,4,42}

我想我以前也遇到过类似的问题，找不到支持库的方法。

PS。发现post-boost:：multi_index_container，在容器内对std:：set进行操作

比较起来很有趣，因为它基本上是在查询时进行类似的间隔合并。这有好处(它保留了插入历史记录，因此您可以查询其他受益于无损耗存储的结果)。它还以插入效率换取更多的查询成本。

我可能会自己编写插入/组合操作。

我试着在这里想出一个描述性的名字。由于操作感觉类似于将"水滴"降落到更大的"水池"中，我将操作称为mix:

template <typename Map, typename V = typename Map::segment_type>
void mix(Map& m, std::initializer_list<V> drops) {
typename Map::codomain_combine combine;
for (auto drop : drops) {
// combine with all overlapping existing segments
auto range = m.equal_range(drop.first);
for (auto it = range.first; it != range.second; ++it) {
combine(drop.second, it->second);
drop.first = hull(drop.first, it->first);
}
m.set(drop); // logically equivalent to m.add(drop) here
}
}

有了这个，你可以清楚地表达你想要的行为，比如：

int main() {
using Map      = boost::icl::interval_map<int, Ints>;
using Interval = Map::interval_type::type;
Map m;
std::cout << m << "n";
mix(m, { {Interval::closed(1,3), {1}},
{Interval::closed(2,4), {2}},
{Interval::closed(5,7), {3}},
{Interval::closed(6,8), {4}} });
std::cout << m << "n";
mix(m, { {Interval::closed(3,6), {42}} }); 
std::cout << m << "n";
}

输出将是

{}
{([1,4]->{1,2,})([5,8]->{3,4,})}
{([1,8]->{1,2,3,4,42,})}

完整演示

在Coliru上直播

#include <boost/icl/interval_map.hpp>
#include <set>
#include <iostream>
template <typename Map, typename V = typename Map::segment_type>
void mix(Map& m, std::initializer_list<V> drops) {
typename Map::codomain_combine combine;
for (auto drop : drops) {
// combine with all overlapping existing segments
auto range = m.equal_range(drop.first);
for (auto it = range.first; it != range.second; ++it) {
combine(drop.second, it->second);
drop.first = hull(drop.first, it->first);
}
m.set(drop); // logically equivalent to m.add(drop) here
}
}
// For debug: an ostreamable std::set<int>
struct Ints : std::set<int> {
using std::set<int>::set;
friend std::ostream& operator<<(std::ostream& os, Ints const& s) {
os << '{';
for(auto i : s) os << i << ",";
return os << '}';
}
};
int main() {
using Map      = boost::icl::interval_map<int, Ints>;
using Interval = Map::interval_type::type;
Map m;
std::cout << m << "n";
mix(m, { {Interval::closed(1,3), {1}},
{Interval::closed(2,4), {2}},
{Interval::closed(5,7), {3}},
{Interval::closed(6,8), {4}} });
std::cout << m << "n";
mix(m, { {Interval::closed(3,6), {42}} }); 
std::cout << m << "n";
}
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