geom_example.C

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/*
                          Aleph_w
 
  Data structures & Algorithms
  version 2.0.0b
  https://github.com/lrleon/Aleph-w
 
  This file is part of Aleph-w library
 
  Copyright (c) 2002-2026 Leandro Rabindranath Leon
 
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:
 
  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
 
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.
*/
 
 
#include <iostream>
#include <iomanip>
#include <cmath>
#include <chrono>
#include <cstring>
 
#include <geom_algorithms.H>
#include <tpl_dynArray.H>
 
using namespace std;
using namespace Aleph;
 
// ============================================================================
// Helper functions
// ============================================================================
 
void print_header(const string& title)
{
  cout << "\n";
  cout << "+" << string(70, '-') << "+" << endl;
  cout << "| " << left << setw(68) << title << " |" << endl;
  cout << "+" << string(70, '-') << "+" << endl;
}
 
void print_subheader(const string& subtitle)
{
  cout << "\n  " << subtitle << endl;
  cout << "  " << string(subtitle.length(), '-') << endl;
}
 
inline double to_double(const Geom_Number& n)
{
  return n.get_d();
}
 
void print_point(const Point& p, const string& label = "")
{
  cout << "  ";
  if (!label.empty()) cout << label << ": ";
  cout << "(" << fixed << setprecision(2) << to_double(p.get_x()) 
       << ", " << to_double(p.get_y()) << ")" << endl;
}
 
void print_polygon(const Polygon& poly, const string& name)
{
  cout << "\n  " << name << " (" << poly.size() << " vertices):" << endl;
  int i = 0;
  for (Polygon::Vertex_Iterator it(poly); it.has_curr(); it.next_ne())
  {
    const Vertex& v = it.get_current_vertex();
    cout << "    V" << i++ << ": (" << fixed << setprecision(2) 
         << to_double(v.get_x()) << ", " << to_double(v.get_y()) << ")" << endl;
  }
}
 
void print_triangle(const Triangle& t, int index)
{
  cout << "    T" << index << ": ";
  const Point& a = t.get_p1();
  const Point& b = t.get_p2();
  const Point& c = t.get_p3();
  cout << "(" << fixed << setprecision(1) 
       << to_double(a.get_x()) << "," << to_double(a.get_y()) << ") - "
       << "(" << to_double(b.get_x()) << "," << to_double(b.get_y()) << ") - "
       << "(" << to_double(c.get_x()) << "," << to_double(c.get_y()) << ")" << endl;
}
 
double triangle_area(const Triangle& t)
{
  const Point& a = t.get_p1();
  const Point& b = t.get_p2();
  const Point& c = t.get_p3();
  
  double ax = to_double(b.get_x()) - to_double(a.get_x());
  double ay = to_double(b.get_y()) - to_double(a.get_y());
  double bx = to_double(c.get_x()) - to_double(a.get_x());
  double by = to_double(c.get_y()) - to_double(a.get_y());
  
  return 0.5 * abs(ax * by - ay * bx);
}
 
// ============================================================================
// Example 1: Basic Polygon Triangulation
// ============================================================================
 
void demo_triangulation_basic()
{
  print_header("Example 1: Polygon Triangulation - Basic Shapes");
  
  // Create a simple square (represents Plaza de Bolivar, Bogota)
  print_subheader("Square (Plaza de Bolivar)");
  
  Polygon square;
  square.add_vertex(Point(0, 0));
  square.add_vertex(Point(100, 0));
  square.add_vertex(Point(100, 100));
  square.add_vertex(Point(0, 100));
  square.close();
  
  print_polygon(square, "Original polygon");
  
  CuttingEarsTriangulation triangulator;
  DynList<Triangle> triangles = triangulator(square);
  
  cout << "\n  Triangulation result:" << endl;
  int i = 0;
  double total_area = 0;
  for (auto it = triangles.get_it(); it.has_curr(); it.next_ne())
  {
    const Triangle& t = it.get_curr();
    print_triangle(t, i++);
    total_area += triangle_area(t);
  }
  
  cout << "\n  Total triangles: " << triangles.size() << endl;
  cout << "  Total area: " << fixed << setprecision(2) << total_area 
       << " square units" << endl;
  cout << "  Expected area: 10000.00 square units" << endl;
  
  // Create a pentagon (star shape simplified)
  print_subheader("Pentagon");
  
  Polygon pentagon;
  double radius = 50;
  for (int j = 0; j < 5; ++j)
  {
    double angle = 2 * M_PI * j / 5 - M_PI / 2;
    pentagon.add_vertex(Point(radius * cos(angle), radius * sin(angle)));
  }
  pentagon.close();
  
  print_polygon(pentagon, "Pentagon");
  
  DynList<Triangle> pent_triangles = triangulator(pentagon);
  
  cout << "\n  Triangulation result:" << endl;
  i = 0;
  total_area = 0;
  for (auto it = pent_triangles.get_it(); it.has_curr(); it.next_ne())
  {
    const Triangle& t = it.get_curr();
    print_triangle(t, i++);
    total_area += triangle_area(t);
  }
  
  cout << "\n  Total triangles: " << pent_triangles.size() << endl;
  cout << "  Total area: " << fixed << setprecision(2) << total_area 
       << " square units" << endl;
}
 
// ============================================================================
// Example 2: Triangulation of Complex Polygon
// ============================================================================
 
void demo_triangulation_complex()
{
  print_header("Example 2: Complex Polygon Triangulation");
  
  // Create an L-shaped polygon (like a building footprint)
  print_subheader("L-shaped polygon (Building footprint)");
  
  Polygon l_shape;
  l_shape.add_vertex(Point(0, 0));
  l_shape.add_vertex(Point(60, 0));
  l_shape.add_vertex(Point(60, 40));
  l_shape.add_vertex(Point(40, 40));
  l_shape.add_vertex(Point(40, 80));
  l_shape.add_vertex(Point(0, 80));
  l_shape.close();
  
  print_polygon(l_shape, "L-shaped polygon");
  
  CuttingEarsTriangulation triangulator;
  DynList<Triangle> triangles = triangulator(l_shape);
  
  cout << "\n  Triangulation result:" << endl;
  int i = 0;
  double total_area = 0;
  for (auto it = triangles.get_it(); it.has_curr(); it.next_ne())
  {
    const Triangle& t = it.get_curr();
    print_triangle(t, i++);
    total_area += triangle_area(t);
  }
  
  cout << "\n  Total triangles: " << triangles.size() << endl;
  cout << "  Total area: " << fixed << setprecision(2) << total_area 
       << " square units" << endl;
  
  // Verify: L-shape area = 60*40 + 40*40 = 2400 + 1600 = 4000
  cout << "  Expected area: 4000.00 square units (60x40 + 40x40)" << endl;
}
 
// ============================================================================
// Example 3: Convex Hull - Colombian Cities
// ============================================================================
 
void demo_convex_hull_cities()
{
  print_header("Example 3: Convex Hull - Colombian Cities");
  
  // Approximate coordinates of Colombian cities (scaled for visibility)
  // Using a simplified coordinate system where (0,0) is near Leticia
  
  DynList<Point> cities;
  
  // Major Colombian cities (approximate positions)
  struct CityCoord { const char* name; double x; double y; };
  DynArray<CityCoord> city_data;
  city_data.append({"Bogota", 74, 44});
  city_data.append({"Medellin", 75, 61});
  city_data.append({"Cali", 76, 34});
  city_data.append({"Barranquilla", 74, 109});
  city_data.append({"Cartagena", 75, 104});
  city_data.append({"Cucuta", 72, 77});
  city_data.append({"Bucaramanga", 73, 71});
  city_data.append({"Pereira", 75, 47});
  city_data.append({"Santa Marta", 74, 111});
  city_data.append({"Ibague", 75, 44});
  city_data.append({"Pasto", 77, 12});
  city_data.append({"Manizales", 75, 51});
  city_data.append({"Villavicencio", 73, 41});
  city_data.append({"Armenia", 75, 44});
  city_data.append({"Leticia", 70, 0});       // Amazon
  city_data.append({"Riohacha", 72, 116});    // La Guajira
  
  cout << "\n  Colombian cities included:" << endl;
  for (size_t i = 0; i < city_data.size(); ++i)
  {
    const auto& c = city_data(i);
    cout << "    " << left << setw(15) << c.name 
         << "(" << c.x << ", " << c.y << ")" << endl;
    cities.append(Point(c.x, c.y));
  }
  
  // Make copies for each algorithm
  DynList<Point> cities_bf, cities_gw, cities_qh;
  for (auto it = cities.get_it(); it.has_curr(); it.next_ne())
  {
    cities_bf.append(it.get_curr());
    cities_gw.append(it.get_curr());
    cities_qh.append(it.get_curr());
  }
  
  // Test each convex hull algorithm
  print_subheader("Brute Force Convex Hull O(n^3)");
  
  BruteForceConvexHull bf_hull;
  auto start = chrono::high_resolution_clock::now();
  Polygon hull_bf = bf_hull(cities_bf);
  auto end = chrono::high_resolution_clock::now();
  auto bf_time = chrono::duration_cast<chrono::microseconds>(end - start).count();
  
  cout << "  Hull vertices: " << hull_bf.size() << endl;
  cout << "  Time: " << bf_time << " microseconds" << endl;
  
  print_subheader("Gift Wrapping Convex Hull O(nh)");
  
  GiftWrappingConvexHull gw_hull;
  start = chrono::high_resolution_clock::now();
  Polygon hull_gw = gw_hull(cities_gw);
  end = chrono::high_resolution_clock::now();
  auto gw_time = chrono::duration_cast<chrono::microseconds>(end - start).count();
  
  cout << "  Hull vertices: " << hull_gw.size() << endl;
  cout << "  Time: " << gw_time << " microseconds" << endl;
  
  print_subheader("QuickHull O(n log n) average");
  
  QuickHull qh_hull;
  start = chrono::high_resolution_clock::now();
  Polygon hull_qh = qh_hull(cities_qh);
  end = chrono::high_resolution_clock::now();
  auto qh_time = chrono::duration_cast<chrono::microseconds>(end - start).count();
  
  cout << "  Hull vertices: " << hull_qh.size() << endl;
  cout << "  Time: " << qh_time << " microseconds" << endl;
  
  // Show which cities are on the border
  print_subheader("Cities on the convex hull (border of Colombia)");
  
  cout << "  The convex hull represents the outermost cities:" << endl;
  for (Polygon::Vertex_Iterator it(hull_qh); it.has_curr(); it.next_ne())
  {
    const Vertex& v = it.get_current_vertex();
    // Find the city name
    for (size_t i = 0; i < city_data.size(); ++i)
    {
      const auto& c = city_data(i);
      if (abs(c.x - to_double(v.get_x())) < 0.5 && 
          abs(c.y - to_double(v.get_y())) < 0.5)
      {
        cout << "    - " << c.name << endl;
        break;
      }
    }
  }
}
 
// ============================================================================
// Example 4: Convex Hull - Random Points Performance
// ============================================================================
 
void demo_convex_hull_performance()
{
  print_header("Example 4: Convex Hull Algorithm Performance");
  
  cout << "\n  Comparing algorithms on random point sets:" << endl;
  cout << "  " << string(60, '-') << endl;
  
  DynArray<int> sizes;
  sizes.append(10);
  sizes.append(50);
  sizes.append(100);
  sizes.append(200);
  
  cout << "\n  " << setw(8) << "Points" 
       << setw(15) << "Brute Force"
       << setw(15) << "Gift Wrap"
       << setw(15) << "QuickHull" 
       << setw(10) << "Hull Size" << endl;
  cout << "  " << string(60, '-') << endl;
  
  for (size_t s = 0; s < sizes.size(); ++s)
  {
    int n = sizes(s);
    
    // Generate random points
    DynList<Point> points_bf, points_gw, points_qh;
    srand(42);  // Fixed seed for reproducibility
    
    for (int i = 0; i < n; ++i)
    {
      double x = (rand() % 1000) / 10.0;
      double y = (rand() % 1000) / 10.0;
      points_bf.append(Point(x, y));
      points_gw.append(Point(x, y));
      points_qh.append(Point(x, y));
    }
    
    // Time each algorithm
    BruteForceConvexHull bf;
    GiftWrappingConvexHull gw;
    QuickHull qh;
    
    auto start = chrono::high_resolution_clock::now();
    Polygon hull_bf = bf(points_bf);
    auto end = chrono::high_resolution_clock::now();
    auto bf_time = chrono::duration_cast<chrono::microseconds>(end - start).count();
    
    start = chrono::high_resolution_clock::now();
    Polygon hull_gw = gw(points_gw);
    end = chrono::high_resolution_clock::now();
    auto gw_time = chrono::duration_cast<chrono::microseconds>(end - start).count();
    
    start = chrono::high_resolution_clock::now();
    Polygon hull_qh = qh(points_qh);
    end = chrono::high_resolution_clock::now();
    auto qh_time = chrono::duration_cast<chrono::microseconds>(end - start).count();
    
    cout << "  " << setw(8) << n
         << setw(12) << bf_time << " us"
         << setw(12) << gw_time << " us"
         << setw(12) << qh_time << " us"
         << setw(10) << hull_qh.size() << endl;
  }
  
  cout << "\n  Note: Times in microseconds (us)" << endl;
  cout << "  Brute Force grows as O(n^3)" << endl;
  cout << "  Gift Wrapping grows as O(nh) where h = hull size" << endl;
  cout << "  QuickHull grows as O(n log n) on average" << endl;
}
 
// ============================================================================
// Example 5: Geometric Primitives Demo
// ============================================================================
 
void demo_geometric_primitives()
{
  print_header("Example 5: Geometric Primitives");
  
  print_subheader("Points and Segments");
  
  // Create some points
  Point bogota(74, 44);
  Point medellin(75, 61);
  Point cali(76, 34);
  
  cout << "  Three major Colombian cities:" << endl;
  print_point(bogota, "Bogota");
  print_point(medellin, "Medellin");
  print_point(cali, "Cali");
  
  // Create segments (routes)
  Segment bogota_medellin(bogota, medellin);
  Segment bogota_cali(bogota, cali);
  
  cout << "\n  Route lengths (approximate):" << endl;
  cout << "    Bogota-Medellin: " << fixed << setprecision(2) 
       << to_double(bogota_medellin.size()) << " units" << endl;
  cout << "    Bogota-Cali: " << to_double(bogota_cali.size()) 
       << " units" << endl;
  
  print_subheader("Point Position Tests");
  
  Point test_point(73, 50);
  cout << "  Test point: (73, 50)" << endl;
  cout << "  Relative to line Bogota-Medellin:" << endl;
  
  if (test_point.is_to_left_from(bogota, medellin))
    cout << "    Point is to the LEFT" << endl;
  else if (test_point.is_to_right_from(bogota, medellin))
    cout << "    Point is to the RIGHT" << endl;
  else
    cout << "    Point is ON the line" << endl;
  
  print_subheader("Triangle Operations");
  
  Triangle triangle(bogota, medellin, cali);
  
  cout << "  Triangle formed by Bogota, Medellin, Cali:" << endl;
  cout << "    Area: " << fixed << setprecision(2) 
       << triangle_area(triangle) << " square units" << endl;
  
  // Check points inside/outside using contains_to
  Point inside(75, 45);   // Somewhere in the middle
  Point outside(80, 80);  // Outside
  
  cout << "\n  Point containment:" << endl;
  cout << "    Point (75, 45): ";
  if (triangle.contains_to(inside))
    cout << "INSIDE the triangle" << endl;
  else
    cout << "OUTSIDE the triangle" << endl;
    
  cout << "    Point (80, 80): ";
  if (triangle.contains_to(outside))
    cout << "INSIDE the triangle" << endl;
  else
    cout << "OUTSIDE the triangle" << endl;
}
 
// ============================================================================
// Example 6: Practical Application - Coverage Area
// ============================================================================
 
void demo_coverage_area()
{
  print_header("Example 6: Coverage Area Calculation");
  
  cout << "\n  Scenario: Calculate coverage area of cell towers" << endl;
  cout << "  " << string(50, '-') << endl;
  
  // Cell tower locations (representing a region in Colombia)
  DynList<Point> towers;
  towers.append(Point(0, 0));
  towers.append(Point(30, 10));
  towers.append(Point(50, 0));
  towers.append(Point(55, 25));
  towers.append(Point(45, 50));
  towers.append(Point(20, 55));
  towers.append(Point(5, 40));
  towers.append(Point(25, 30));  // Interior tower
  towers.append(Point(35, 25));  // Interior tower
  
  cout << "\n  Tower locations:" << endl;
  int tower_num = 1;
  for (auto it = towers.get_it(); it.has_curr(); it.next_ne())
  {
    const Point& p = it.get_curr();
    cout << "    Tower " << tower_num++ << ": (" 
         << to_double(p.get_x()) << ", " 
         << to_double(p.get_y()) << ")" << endl;
  }
  
  // Calculate convex hull (coverage boundary)
  QuickHull qh;
  Polygon coverage = qh(towers);
  
  cout << "\n  Coverage boundary (convex hull):" << endl;
  cout << "    Boundary towers: " << coverage.size() << endl;
  cout << "    Interior towers: " << (9 - coverage.size()) << endl;
  
  // Calculate coverage area using triangulation
  Polygon coverage_copy = coverage;  // triangulation consumes the polygon
  CuttingEarsTriangulation triangulator;
  DynList<Triangle> triangles = triangulator(coverage_copy);
  
  double total_area = 0;
  for (auto it = triangles.get_it(); it.has_curr(); it.next_ne())
    total_area += triangle_area(it.get_curr());
  
  cout << "\n  Coverage statistics:" << endl;
  cout << "    Total coverage area: " << fixed << setprecision(2) 
       << total_area << " square km" << endl;
  cout << "    Triangles in mesh: " << triangles.size() << endl;
  
  // Perimeter calculation
  double perimeter = 0;
  for (Polygon::Segment_Iterator it(coverage); it.has_curr(); it.next_ne())
  {
    const Segment& seg = it.get_current_segment();
    perimeter += to_double(seg.size());
  }
  
  cout << "    Perimeter: " << perimeter << " km" << endl;
  cout << "    Compactness ratio: " << (4 * M_PI * total_area) / (perimeter * perimeter)
       << " (1.0 = circle)" << endl;
}
 
// ============================================================================
// Main
// ============================================================================
 
static void usage(const char* prog)
{
  cout << "Usage: " << prog << " [-s <triangulation|convexhull|all>] [--help]\n";
  cout << "\nIf no selector is given, all demos are executed.\n";
}
 
int main(int argc, char* argv[])
{
  string section = "all";
  for (int i = 1; i < argc; ++i)
    {
      const string arg = argv[i];
      if (arg == "--help" || arg == "-h")
        {
          usage(argv[0]);
          return 0;
        }
      if (arg == "-s")
        {
          if (i + 1 >= argc)
            {
              usage(argv[0]);
              return 1;
            }
          section = argv[++i];
          continue;
        }
 
      cout << "Unknown argument: " << arg << "\n";
      usage(argv[0]);
      return 1;
    }
 
  cout << "\n";
  cout << "========================================================================" << endl;
  cout << "        ALEPH-W COMPUTATIONAL GEOMETRY EXAMPLE" << endl;
  cout << "        Triangulation and Convex Hull Algorithms" << endl;
  cout << "========================================================================" << endl;
 
  if (section == "all" || section == "triangulation")
    {
      demo_triangulation_basic();
      demo_triangulation_complex();
    }
 
  if (section == "all" || section == "convexhull")
    {
      demo_convex_hull_cities();
      demo_convex_hull_performance();
    }
 
  if (section == "all")
    {
      demo_geometric_primitives();
      demo_coverage_area();
    }
 
  if (!(section == "all" || section == "triangulation" || section == "convexhull"))
    {
      cout << "Unknown section: " << section << "\n";
      usage(argv[0]);
      return 1;
    }
  
  cout << "\n";
  cout << "========================================================================" << endl;
  cout << "                    Example completed successfully!" << endl;
  cout << "========================================================================" << endl;
  cout << endl;
  
  return 0;
}