2024/23

encse · encse · commit b8b2c709867b · 2024-12-23T12:03:46.000+01:00
diff --git a/2024/Day23/README.md b/2024/Day23/README.md
@@ -7,4 +7,4 @@ _Visit the website for the full story and [full puzzle](https://adventofcode.com
 
 We tackled a graph algorithm problem today, where we had to find maximal cliques in an undirected graph. The literature provides [efficient algorithms](https://en.wikipedia.org/wiki/Bron%E2%80%93Kerbosch_algorithm) for this problem, but our graph is not too large, so we can use a straightforward "poor man's" strategy as well. 
 
-I started with the _seed_ components, that is single element components for each node that starts with '_t_'. Then, I proceeded to _grow_ these components by adding a single node to them in all possible ways. I can put this in a loop, to get components with size 2, 3, 4, etc. _Part 1_ asks for the number of components that have 3 nodes. _Part 2_ asks for the one that cannot be grown anymore. 
+I started with the _seed_ components, that is single element components for each node. Then, I proceeded to _grow_ these components by adding a single node to them in all possible ways. I can put this in a loop, to get components with size 2, 3, 4, etc. _Part 1_ asks for the number of components that have 3 nodes and have at least one node starting with 't'. _Part 2_ asks for the biggest component that cannot be grown anymore. 
diff --git a/2024/Day23/Solution.cs b/2024/Day23/Solution.cs
@@ -14,7 +14,7 @@ public object PartOne(string input) {
         var components = GetSeed(g);
         components = Grow(g, components);
         components = Grow(g, components);
-        return components.Count;
+        return components.Count(c => Members(c).Any(m=>m.StartsWith("t")));
     }
 
     public object PartTwo(string input) {
@@ -26,10 +26,10 @@ public object PartTwo(string input) {
         return components.Single();
     }
 
-    HashSet<Component> GetSeed(Graph g) => g.Keys.Where(k=>k.StartsWith("t")).ToHashSet();
+    HashSet<Component> GetSeed(Graph g) => g.Keys.ToHashSet();
     
     HashSet<Component> Grow(Graph g, HashSet<Component> components) => (
-        from c in components
+        from c in components.AsParallel()
         let members = Members(c)
         from neighbour in members.SelectMany(m => g[m]).Distinct()
         where !members.Contains(neighbour)

Original file line number	Diff line number	Diff line change
`@@ -7,4 +7,4 @@ _Visit the website for the full story and [full puzzle](https://adventofcode.com`
`7`	`7`
`8`	`8`	`We tackled a graph algorithm problem today, where we had to find maximal cliques in an undirected graph. The literature provides [efficient algorithms](https://en.wikipedia.org/wiki/Bron%E2%80%93Kerbosch_algorithm) for this problem, but our graph is not too large, so we can use a straightforward "poor man's" strategy as well.`
`9`	`9`
`10`		`-I started with the _seed_ components, that is single element components for each node that starts with '_t_'. Then, I proceeded to _grow_ these components by adding a single node to them in all possible ways. I can put this in a loop, to get components with size 2, 3, 4, etc. _Part 1_ asks for the number of components that have 3 nodes. _Part 2_ asks for the one that cannot be grown anymore.`
	`10`	`+I started with the _seed_ components, that is single element components for each node. Then, I proceeded to _grow_ these components by adding a single node to them in all possible ways. I can put this in a loop, to get components with size 2, 3, 4, etc. _Part 1_ asks for the number of components that have 3 nodes and have at least one node starting with 't'. _Part 2_ asks for the biggest component that cannot be grown anymore.`