rectangle-union-area/segment_tree.h

//
// Created by maximilian on 16.04.22.
//

#include<vector>
#include "geometry.h"

#ifndef PROG_SEGMENT_TREE_H
#define PROG_SEGMENT_TREE_H


struct TreeNode {
    unsigned coverage;
    Coordinate left_coord;
    Coordinate right_coord;
    Unit covered_length;
    inline Unit segment_length();
};


class SegmentTree {
    std::vector<TreeNode> _nodes;
public:
    /**
     *
     * @param coords Sorted vector of coordinates
     */
    SegmentTree(const std::vector<RectCoord>& coords);

    inline Unit length_covered_intervals();
    inline void add_interval(Interval interval);
    inline void remove_interval(Interval interval);

private:
    inline static Index left_child_idx(Index node_idx);
    inline static Index right_child_idx(Index node_idx);
    inline TreeNode& left_child(Index node_idx);
    inline TreeNode& right_child(Index node_idx);
    inline void add_coverage(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 remove_interval(Interval interval, Index node_idx);

};

/*****************************************************
 * INLINE section
 ****************************************************/



TreeNode& SegmentTree::left_child(Index node_idx) {
    return _nodes[left_child_idx(node_idx)];
}

TreeNode& SegmentTree::right_child(Index node_idx) {
    return _nodes[right_child_idx(node_idx)];
}

Unit SegmentTree::length_covered_intervals() {
    return _nodes.front().covered_length;
}

void SegmentTree::add_interval(Interval interval) {
    add_interval(interval, 0);
}

void SegmentTree::remove_interval(Interval interval) {
    remove_interval(interval, 0);
}

void SegmentTree::add_coverage(Index node_idx) {
    ++(_nodes[node_idx].coverage);
    update_covered_length(node_idx);
}

void SegmentTree::remove_coverage(Index node_idx) {
    --(_nodes[node_idx].coverage);
    update_covered_length(node_idx);
}

Index SegmentTree::left_child_idx(Index node_idx) {
    return 2*node_idx + 1;
}

Index SegmentTree::right_child_idx(Index node_idx) {
    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() {
    return right_coord - left_coord;
}


#endif //PROG_SEGMENT_TREE_H