Added: code to check for duplicates

Arrangement_on_surface_2/demo/earth/Kml_reader.cpp

@@ -2,6 +2,7 @@
 #include "Kml_reader.h"
 
 #include <iostream>
+#include <unordered_map>
 
 #include <qdebug.h>
 #include <qfile.h>
@@ -98,3 +99,63 @@ Kml::Placemarks  Kml::read(const std::string& file_name)
 
   return placemarks;
 }
+
+void Kml::check_duplicates(const Placemarks& placemarks)
+{
+  // collect all nodes into a single vector
+  int polygon_count = 0;
+  std::vector<Kml::Node> nodes;
+  for (const auto& pm : placemarks)
+  {
+    for (const auto& pg : pm.polygons)
+    {
+      polygon_count++;
+      for (const auto& node : pg.nodes)
+        nodes.push_back(node);
+    }
+  }
+  qDebug() << "polygon count = " << polygon_count;
+
+  int count = nodes.size();
+  std::vector<int> num_duplicates(count, 0);
+  qDebug() << "node count (with duplicates) = " << count;
+  int dup_count = 0;
+
+  // this keeps track of how many nodes there are with certain dup-count
+  std::unordered_map<int, int> dup_count_map;
+
+  for (int i = 0; i < count; ++i)
+  {
+    // if the current node has been detected as duplicate skip it
+    if (num_duplicates[i] > 0)
+      continue;
+
+    std::vector<int> curr_dup; // current set of duplicates
+    for (int j = i + 1; j < count; ++j)
+    {
+      if (nodes[i] == nodes[j])
+      {
+        curr_dup.push_back(j);
+      }
+    }
+
+    // if duplicates found
+    if (!curr_dup.empty())
+    {
+      dup_count++;
+      int num_dup = curr_dup.size() + 1; // +1 for the i'th node
+      num_duplicates[i] = num_dup;
+      for (const auto di : curr_dup)
+        num_duplicates[di] = num_dup;
+
+      dup_count_map[num_dup]++;
+    }
+  }
+  qDebug() << "dup count = " << dup_count;
+  for (const auto& p : dup_count_map)
+  {
+    const auto dup_count = p.first;
+    const auto num_nodes_with_this_dup_count = p.second;
+    qDebug() << dup_count << ": " << num_nodes_with_this_dup_count;
+  }
+}

Arrangement_on_surface_2/demo/earth/Kml_reader.h

@@ -12,6 +12,11 @@ class Kml
   struct Node
   {
     double lon, lat;
+
+    bool operator == (const Node& r) 
+    { 
+      return  (lon == r.lon) && (lat == r.lat);
+    }
   };
 
   struct LinearRing
@@ -30,6 +35,8 @@ class Kml
 
 
   static Placemarks read(const std::string& file_name);
+
+  static void check_duplicates(const Placemarks& placemarks);
 };
 
 

Arrangement_on_surface_2/demo/earth/Main_widget.cpp

@@ -106,10 +106,12 @@ void Main_widget::timerEvent(QTimerEvent*)
   update();
 }
 
+
 void Main_widget::initializeGL()
 {
   const auto file_name = "C:/work/gsoc2023/data/world_countries.kml";
   auto countries = Kml::read(file_name);
+  Kml::check_duplicates(countries);
 
 
   initializeOpenGLFunctions();