max/rectangle-union-area
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add bottom case when updating covered lengths

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Maximilian Keßler 2022-04-16 13:16:34 +02:00
parent 3df8c5095d
commit 647d1da843
3 changed files with 24 additions and 14 deletions
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6
main.cpp
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@ -27,6 +27,12 @@ int main() {
add_rect(3,2,6,6); add_rect(3,2,6,6);
check_area(28); check_area(28);
add_rect(1,-2,8,4);
check_area(52);
add_rect(2,2,7,3);
check_area(52);
std::cout << "All checks passed" << std::endl; std::cout << "All checks passed" << std::endl;
return 0; return 0;
} }

20
segment_tree.cpp
View file

@ -6,26 +6,24 @@
#include "segment_tree.h" #include "segment_tree.h"
SegmentTree::SegmentTree(const std::vector<RectCoord> &coords): SegmentTree::SegmentTree(const std::vector<RectCoord> &coords):
_nodes() { _num_leaf_nodes(coords.size() -1),
// reserve nodes for a full binary tree with at least as many leaves as intervals
_num_meta_nodes(std::bit_ceil(_num_leaf_nodes) -1),
_nodes(2 * _num_meta_nodes + 1, {0, coords[_num_leaf_nodes].coord, coords[_num_leaf_nodes].coord, 0}) {
assert(!coords.empty()); assert(!coords.empty());
// reserve nodes for a full binary tree with at least as many leaves as intervals
size_t num_leaf_nodes = coords.size() -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, 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
for(Index leaf_node_idx = 0 ; leaf_node_idx < num_leaf_nodes ; ++leaf_node_idx) { for(Index leaf_node_idx = 0 ; leaf_node_idx < _num_leaf_nodes ; ++leaf_node_idx) {
_nodes[leaf_node_idx + num_meta_nodes].left_coord = coords[leaf_node_idx].coord; _nodes[leaf_node_idx + _num_meta_nodes].left_coord = coords[leaf_node_idx].coord;
_nodes[leaf_node_idx + num_meta_nodes].right_coord = coords[leaf_node_idx +1].coord; _nodes[leaf_node_idx + _num_meta_nodes].right_coord = coords[leaf_node_idx + 1].coord;
} }
// Note that there are remaining leafs that represent dummy ranges // Note that there are remaining leafs that represent dummy ranges
for(Index node_idx = num_meta_nodes - 1; node_idx != -1 ; --node_idx) { for(Index node_idx = _num_meta_nodes - 1; node_idx != -1 ; --node_idx) {
_nodes[node_idx].left_coord = left_child(node_idx).left_coord; _nodes[node_idx].left_coord = left_child(node_idx).left_coord;
_nodes[node_idx].right_coord = right_child(node_idx).right_coord; _nodes[node_idx].right_coord = right_child(node_idx).right_coord;
} }
@ -62,5 +60,3 @@ void SegmentTree::remove_interval(Interval interval, Index node_idx) {
update_covered_length(node_idx); update_covered_length(node_idx);
} }
} }

10
segment_tree.h
View file

@ -19,6 +19,8 @@ struct TreeNode {
class SegmentTree { class SegmentTree {
size_t _num_leaf_nodes;
size_t _num_meta_nodes;
std::vector<TreeNode> _nodes; std::vector<TreeNode> _nodes;
public: public:
/** /**
@ -41,6 +43,7 @@ private:
inline void update_covered_length(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);
inline bool is_leaf(Index node_idx);
}; };
@ -91,16 +94,21 @@ Index SegmentTree::right_child_idx(Index node_idx) {
void SegmentTree::update_covered_length(Index node_idx) { void SegmentTree::update_covered_length(Index node_idx) {
if (_nodes[node_idx].coverage > 0) { if (_nodes[node_idx].coverage > 0) {
_nodes[node_idx].covered_length = _nodes[node_idx].segment_length(); _nodes[node_idx].covered_length = _nodes[node_idx].segment_length();
} else if (is_leaf(node_idx)) {
_nodes[node_idx].covered_length = 0;
} else { } else {
_nodes[node_idx].covered_length = \ _nodes[node_idx].covered_length = \
left_child(node_idx).covered_length + right_child(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;
} }
bool SegmentTree::is_leaf(Index node_idx) {
return node_idx > _num_meta_nodes;
}
#endif //PROG_SEGMENT_TREE_H #endif //PROG_SEGMENT_TREE_H