max/rectangle-union-area
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store covered length at each node separately

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This commit is contained in:
Maximilian Keßler 2022-04-16 12:29:01 +02:00
parent 9bc33b22e9
commit a4c035b6dc
2 changed files with 23 additions and 16 deletions
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9
segment_tree.cpp
View File

@ -6,7 +6,7 @@
#include "segment_tree.h" #include "segment_tree.h"
SegmentTree::SegmentTree(const std::vector<RectCoord> &coords): SegmentTree::SegmentTree(const std::vector<RectCoord> &coords):
_covered_cross_section_length(0), _nodes() { _nodes() {
assert(!coords.empty()); assert(!coords.empty());
@ -15,7 +15,7 @@ SegmentTree::SegmentTree(const std::vector<RectCoord> &coords):
size_t num_meta_nodes = std::bit_ceil(num_leaf_nodes) - 1; size_t num_meta_nodes = std::bit_ceil(num_leaf_nodes) - 1;
// Initialize all nodes with zero coverage and dummy interval // Initialize all nodes with zero coverage and dummy interval
_nodes.resize(2 * num_meta_nodes + 1, {0, coords[num_leaf_nodes].coord, coords[num_leaf_nodes].coord}); _nodes.resize(2 * num_meta_nodes + 1, {0, coords[num_leaf_nodes].coord, coords[num_leaf_nodes].coord, 0});
// We initialize the tree from bottom up, keeping track of the index ranges // We initialize the tree from bottom up, keeping track of the index ranges
// and the length of the corresponding segment // and the length of the corresponding segment
@ -37,7 +37,7 @@ SegmentTree::SegmentTree(const std::vector<RectCoord> &coords):
void SegmentTree::add_interval(Interval interval, Index node_idx) { void SegmentTree::add_interval(Interval interval, Index node_idx) {
if (interval.left <= _nodes[node_idx].left_coord && _nodes[node_idx].right_coord <= interval.right) { if (interval.left <= _nodes[node_idx].left_coord && _nodes[node_idx].right_coord <= interval.right) {
update_added(node_idx); add_coverage(node_idx);
} else { } else {
if(interval.left < left_child(node_idx).right_coord) { if(interval.left < left_child(node_idx).right_coord) {
add_interval(interval, left_child_idx(node_idx)); add_interval(interval, left_child_idx(node_idx));
@ -45,12 +45,13 @@ void SegmentTree::add_interval(Interval interval, Index node_idx) {
if(right_child(node_idx).left_coord < interval.right) { if(right_child(node_idx).left_coord < interval.right) {
add_interval(interval, right_child_idx(node_idx)); add_interval(interval, right_child_idx(node_idx));
} }
update_covered_length(node_idx);
} }
} }
void SegmentTree::remove_interval(Interval interval, Index node_idx) { void SegmentTree::remove_interval(Interval interval, Index node_idx) {
if (interval.left <= _nodes[node_idx].left_coord && _nodes[node_idx].right_coord <= interval.right) { if (interval.left <= _nodes[node_idx].left_coord && _nodes[node_idx].right_coord <= interval.right) {
update_removed(node_idx); remove_coverage(node_idx);
} else { } else {
if(interval.left < left_child(node_idx).right_coord) { if(interval.left < left_child(node_idx).right_coord) {
remove_interval(interval, left_child_idx(node_idx)); remove_interval(interval, left_child_idx(node_idx));

30
segment_tree.h
View File

@ -13,13 +13,13 @@ struct TreeNode {
unsigned coverage; unsigned coverage;
Coordinate left_coord; Coordinate left_coord;
Coordinate right_coord; Coordinate right_coord;
Unit covered_length;
inline Unit segment_length(); inline Unit segment_length();
}; };
class SegmentTree { class SegmentTree {
std::vector<TreeNode> _nodes; std::vector<TreeNode> _nodes;
Unit _covered_cross_section_length;
public: public:
/** /**
* *
@ -36,8 +36,9 @@ private:
inline static Index right_child_idx(Index node_idx); inline static Index right_child_idx(Index node_idx);
inline TreeNode& left_child(Index node_idx); inline TreeNode& left_child(Index node_idx);
inline TreeNode& right_child(Index node_idx); inline TreeNode& right_child(Index node_idx);
inline void update_added(Index node_idx); inline void add_coverage(Index node_idx);
inline void update_removed(Index node_idx); inline void remove_coverage(Index node_idx);
inline void update_covered_length(Index node_idx);
void add_interval(Interval interval, Index node_idx); void add_interval(Interval interval, Index node_idx);
void remove_interval(Interval interval, Index node_idx); void remove_interval(Interval interval, Index node_idx);
@ -58,7 +59,7 @@ TreeNode& SegmentTree::right_child(Index node_idx) {
} }
Unit SegmentTree::length_covered_intervals() { Unit SegmentTree::length_covered_intervals() {
return _covered_cross_section_length; return _nodes.front().covered_length;
} }
void SegmentTree::add_interval(Interval interval) { void SegmentTree::add_interval(Interval interval) {
@ -69,18 +70,14 @@ void SegmentTree::remove_interval(Interval interval) {
remove_interval(interval, 0); remove_interval(interval, 0);
} }
void SegmentTree::update_added(Index node_idx) { void SegmentTree::add_coverage(Index node_idx) {
++(_nodes[node_idx].coverage); ++(_nodes[node_idx].coverage);
if(_nodes[node_idx].coverage == 1) { update_covered_length(node_idx);
_covered_cross_section_length += _nodes[node_idx].segment_length();
}
} }
void SegmentTree::update_removed(Index node_idx) { void SegmentTree::remove_coverage(Index node_idx) {
--(_nodes[node_idx].coverage); --(_nodes[node_idx].coverage);
if(_nodes[node_idx].coverage == 0) { update_covered_length(node_idx);
_covered_cross_section_length -= _nodes[node_idx].segment_length();
}
} }
Index SegmentTree::left_child_idx(Index node_idx) { Index SegmentTree::left_child_idx(Index node_idx) {
@ -91,6 +88,15 @@ Index SegmentTree::right_child_idx(Index node_idx) {
return 2*node_idx + 2; return 2*node_idx + 2;
} }
void SegmentTree::update_covered_length(Index node_idx) {
if (_nodes[node_idx].coverage > 0) {
_nodes[node_idx].covered_length = _nodes[node_idx].segment_length();
} else {
_nodes[node_idx].covered_length = \
left_child(node_idx).covered_length + right_child(node_idx).covered_length;
}
}
Unit TreeNode::segment_length() { Unit TreeNode::segment_length() {
return right_coord - left_coord; return right_coord - left_coord;