D23.2 OK but not a very good algorithm ...

Adv2018.sln

@@ -93,6 +93,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "D22.2", "D22.2\D22.2.csproj
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "D23.1", "D23.1\D23.1.csproj", "{107344C3-3FFF-45D1-B709-BF382C1F7E9A}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "D23.2", "D23.2\D23.2.csproj", "{8B805697-82CB-435D-8329-BC67ACA04B5D}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -279,6 +281,10 @@ Global
 		{107344C3-3FFF-45D1-B709-BF382C1F7E9A}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{107344C3-3FFF-45D1-B709-BF382C1F7E9A}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{107344C3-3FFF-45D1-B709-BF382C1F7E9A}.Release|Any CPU.Build.0 = Release|Any CPU
+		{8B805697-82CB-435D-8329-BC67ACA04B5D}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{8B805697-82CB-435D-8329-BC67ACA04B5D}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{8B805697-82CB-435D-8329-BC67ACA04B5D}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{8B805697-82CB-435D-8329-BC67ACA04B5D}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE

D23.2/D23.2.csproj

@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>netcoreapp2.1</TargetFramework>
+    <RootNamespace>D23._2</RootNamespace>
+    <LangVersion>7.3</LangVersion>
+  </PropertyGroup>
+
+</Project>

D23.2/Program.cs

@@ -0,0 +1,136 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text.RegularExpressions;
+
+namespace D23._2
+{
+    class Program
+    {
+        static int Manhattan((int x, int y, int z) a, (int x, int y, int z) b)
+        {
+            return Math.Abs(a.x - b.x) + Math.Abs(a.y - b.y) + Math.Abs(a.z - b.z);
+        }
+
+        static int InRange(List<(int x, int y, int z, int r)> nanoList, (int x, int y, int z) coord)
+        {
+            int count = 0;
+            foreach (var n in nanoList)
+            {
+                int m = Manhattan(coord, (n.x, n.y, n.z));
+                if (m <= n.r) count++;
+            }
+            return count;
+        }
+
+        static HashSet<(int x, int y, int z)> tested = new HashSet<(int x, int y, int z)>();
+        static (int, (int, int, int)) Test(List<(int x, int y, int z, int r)> nanoList, (int x, int y, int z) coord, int i)
+        {
+            var point = coord;
+            var stack = new List<((int x, int y, int z) pos, int count)>();
+
+            int maxCount = 0;
+            (int x, int y, int z) bestPosition = coord;
+            int manhattanBest = 0;
+
+            stack.Add((point, 0));
+
+            while (stack.Count > 0)
+            {
+                stack.Sort((a, b) => b.count.CompareTo(a.count));
+
+                var first = stack.First();
+                point = first.pos;
+                stack.Remove(first);
+
+                tested.Add(point);
+
+                var count = InRange(nanoList, point);
+                if (count > maxCount)
+                {
+                    maxCount = count;
+                    bestPosition = point;
+                    manhattanBest = Manhattan(point, (0, 0, 0));
+                    stack.RemoveAll(s => s.count < maxCount);
+                    Console.Write($"Best is {maxCount} - Manhattan {manhattanBest}                 \r");
+                }
+                else if (count == maxCount)
+                {
+                    var pmanhattan = Manhattan(point, (0, 0, 0));
+                    if (pmanhattan < manhattanBest)
+                    {
+                        bestPosition = point;
+                        manhattanBest = pmanhattan;
+                        stack.RemoveAll(s => s.count < maxCount);
+                        Console.Write($"Best is {maxCount} - Manhattan {manhattanBest}                 \r");
+                    }
+                }
+                else continue;
+
+                foreach (var (mx, my, mz) in MovementList)
+                {
+                    var mpoint = (point.x + mx * i, point.y + my * i, point.z + mz * i);
+                    if (tested.Contains(mpoint)) continue;
+                    if (stack.Contains((mpoint, count))) continue;
+                    stack.Add((mpoint, count));
+                }
+            }
+
+            return (manhattanBest, bestPosition);
+        }
+
+        static (int mx, int my, int mz)[] MovementList = new[] { (0, -1, 0), (0, 1, 0), (-1, 0, 0), (1, 0, 0), (0, 0, -1), (0, 0, 1) };
+        static void Main(string[] args)
+        {
+            if (args.Length < 1) return;
+            if (File.Exists(args[0]) == false) return;
+
+            var file = File.OpenText(args[0]);
+
+            var reg = new Regex(@"pos=<([\d-,]+)>, r=(\d+)");
+
+            var nanoList = new List<(int x, int y, int z, int r)>();
+
+            do
+            {
+                var line = file.ReadLine();
+                if (line == null) break;
+
+                var res = reg.Match(line);
+
+                var xyz = res.Groups[1].Value.Split(",").Select(s => int.Parse(s)).ToArray();
+                var r = int.Parse(res.Groups[2].Value);
+
+                nanoList.Add((xyz[0], xyz[1], xyz[2], r));
+            } while (true);
+
+            file.Close();
+
+            int inRange = 0;
+            (int, int, int) best = (0, 0, 0);
+            foreach (var n in nanoList)
+            {
+                int m = InRange(nanoList, (n.x, n.y, n.z));
+                if (m > inRange)
+                {
+                    inRange = m;
+                    best = (n.x, n.y, n.z);
+                }
+            }
+
+            int bestManhattant = 0;
+            for (var i = (int) Math.Pow(2, 16); i >= 1; i /= 2)
+            {
+                Console.Clear();
+                Console.WriteLine($"Testing with i = {i}");
+
+                (var manhattan, var nbest) = Test(nanoList, best, i);
+                best = nbest;
+                bestManhattant = manhattan;
+            }
+
+            Console.WriteLine($"\nAnswer is : {bestManhattant}");
+        }
+    }
+}

D23.2/Properties/launchSettings.json

@@ -0,0 +1,8 @@
+{
+  "profiles": {
+    "D23.2": {
+      "commandName": "Project",
+      "commandLineArgs": "\"..\\..\\..\\..\\D23.1\\input.txt\" "
+    }
+  }
+}