Solution for day 7 in C#.

2025-12-25 21:00:31 +01:00 · 2017-12-07 12:49:16 +01:00
parent 5b53308a8d
commit 10b40b5808
2 changed files with 1526 additions and 0 deletions
--- a/2017/day-07/solution.cs
+++ b/2017/day-07/solution.cs
@@ -0,0 +1,108 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+public class Solution {
+
+	static public void Main ()
+	{
+		Dictionary<string, string> parents = new Dictionary<string, string>();
+		Dictionary<string, int> weights = new Dictionary<string, int>();
+		Dictionary<string, HashSet<string>> children = new Dictionary<string, HashSet<string>>();
+
+		string line = Console.ReadLine();
+		do {
+			line = line.Trim();
+			string[] parts = line.Split(new string[] {" -> "}, StringSplitOptions.None);
+			string[] nodeInfoParts = parts[0].Split(new char[] {' '});
+			string parent = nodeInfoParts[0];
+			int weight = int.Parse(nodeInfoParts[1].Substring(1, nodeInfoParts[1].Length - 2));
+
+			weights.Add(parent, weight);
+			children.Add(parent, new HashSet<string>());
+
+			if (parts.Length == 2) {
+				string[] curChildren = parts[1].Trim().Split(new string[] {", "}, StringSplitOptions.None);
+
+				foreach (string child in curChildren) {
+					parents.Add(child, parent);
+					children[parent].Add(child);
+				}
+			}
+
+			line = Console.ReadLine();
+		} while (line != null);
+
+		string root = RootNode(parents);
+		Console.WriteLine(root);
+		WrongWeight(root, children, weights);
+	}
+
+	static private string RootNode(Dictionary<string, string> parents) {
+		string current = parents.Keys.First();
+
+		while (parents.ContainsKey(current)) {
+			current = parents[current];
+		}
+
+		return current;
+	}
+
+	static private void WrongWeight(string root, Dictionary<string, HashSet<string>> children, Dictionary<string, int> weights) {
+		try {
+			TowerWeight(root, children, weights);
+		} catch (System.ArgumentException ex) {
+			// Do nothing
+		}
+	}
+
+
+	static private int TowerWeight(string current, Dictionary<string, HashSet<string>> children, Dictionary<string, int> weights) {
+		if (children[current].Count == 0) {
+			return weights[current];
+		}
+
+		int[] childWeights = new int[children[current].Count];
+		string[] childNames = new string[children[current].Count];
+
+		int i = 0;
+		foreach (string child in children[current]) {
+			int weight = TowerWeight(child, children, weights);
+			childWeights[i] = weight;
+			childNames[i] = child;
+			i++;
+		}
+
+		int misMatches = 0;
+		int misMatchIndex = -1;
+		for (i = 1; i < children[current].Count; i++) {
+			if (childWeights[i] != childWeights[0]) {
+				misMatches++;
+				misMatchIndex = i;
+			}
+		}
+
+		int wrongIndex;
+		int delta;
+		switch (misMatches) {
+			case 0:
+				int finalWeight = children[current].Count * childWeights[0] + weights[current];
+				// Tower is okay
+				return finalWeight;
+
+			case 1:
+				wrongIndex = misMatchIndex;
+				delta = childWeights[misMatchIndex] - childWeights[0];
+				break;
+
+			default:
+				wrongIndex = 0;
+				delta = childWeights[0] - childWeights[1];
+				break;
+		}
+
+		Console.WriteLine(childNames[wrongIndex] + " " + (weights[childNames[wrongIndex]] - delta));
+
+		throw new ArgumentException(current);
+	}
+}