java/2016/10: add solution for part 1

Author: saser

java/src/main/java/com/github/saser/adventofcode/year2016/day10/Day10.java

@@ -1,6 +1,14 @@
 package com.github.saser.adventofcode.year2016.day10;
 
+import java.io.BufferedReader;
 import java.io.Reader;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.regex.Pattern;
 
 import com.github.saser.adventofcode.Result;
 
@@ -14,6 +22,128 @@ public static Result part2(Reader r) {
     }
 
     private static Result solve(Reader r, int part) {
+        var network = Network.parse(r);
+        var paths = network.flow();
+        if (part == 1) {
+            var visited61 = new HashSet<>(paths.get(61));
+            var visited17 = new HashSet<>(paths.get(17));
+            visited61.retainAll(visited17);
+            var bot = visited61.iterator().next();
+            return Result.ok(Integer.toString(bot));
+        }
         return Result.err("not implemented yet");
     }
+
+    private static class Network {
+        public final Map<Integer, Sink> sources;
+        public final Map<Integer, Sink> highSinks;
+        public final Map<Integer, Sink> lowSinks;
+
+        public Network(Map<Integer, Sink> sources, Map<Integer, Sink> highSinks, Map<Integer, Sink> lowSinks) {
+            this.sources = sources;
+            this.highSinks = highSinks;
+            this.lowSinks = lowSinks;
+        }
+
+        public static Network parse(Reader r) {
+            var sources = new HashMap<Integer, Sink>();
+            var highSinks = new HashMap<Integer, Sink>();
+            var lowSinks = new HashMap<Integer, Sink>();
+            var br = new BufferedReader(r);
+            var it = br.lines().iterator();
+            var sourceRE = Pattern.compile("value (\\d+) goes to bot (\\d+)");
+            var highLowRE = Pattern.compile("bot (\\d+) gives (low|high) to (output|bot) (\\d+) and (low|high) to (output|bot) (\\d+)");
+            while (it.hasNext()) {
+                var line = it.next();
+                var sourceMatcher = sourceRE.matcher(line);
+                if (sourceMatcher.matches()) {
+                    var value = Integer.parseInt(sourceMatcher.group(1));
+                    var bot = Integer.parseInt(sourceMatcher.group(2));
+                    sources.put(value, new Sink(bot, false));
+                    continue;
+                }
+                var highLowMatcher = highLowRE.matcher(line);
+                if (highLowMatcher.matches()) {
+                    var sourceBot = Integer.parseInt(highLowMatcher.group(1));
+                    var isLow1 = highLowMatcher.group(2).equals("low");
+                    var isOutput1 = highLowMatcher.group(3).equals("output");
+                    var number1 = Integer.parseInt(highLowMatcher.group(4));
+                    (isLow1 ? lowSinks : highSinks).put(sourceBot, new Sink(number1, isOutput1));
+                    var isLow2 = highLowMatcher.group(5).equals("low");
+                    var isOutput2 = highLowMatcher.group(6).equals("output");
+                    var number2 = Integer.parseInt(highLowMatcher.group(7));
+                    (isLow2 ? lowSinks : highSinks).put(sourceBot, new Sink(number2, isOutput2));
+                    continue;
+                }
+                throw new IllegalArgumentException(String.format("invalid line: %s", line));
+            }
+            return new Network(sources, highSinks, lowSinks);
+        }
+
+        public Map<Integer, List<Integer>> flow() {
+            var q = new LinkedList<Pair<Integer, Sink>>();
+            for (var entry : this.sources.entrySet()) {
+                q.add(new Pair<>(entry.getKey(), entry.getValue()));
+            }
+            var paths = new HashMap<Integer, List<Integer>>();
+            var held = new HashMap<Integer, Integer>();
+            while (!q.isEmpty()) {
+                var entry = q.removeFirst();
+                var value = entry.first;
+                var sink = entry.second;
+                if (!paths.containsKey(value)) {
+                    paths.put(value, new LinkedList<>());
+                }
+                paths.get(value).add(sink.target);
+                if (sink.isOutput) {
+                    continue;
+                }
+                var bot = sink.target;
+                if (!held.containsKey(bot)) {
+                    held.put(bot, value);
+                    continue;
+                }
+                var current = held.get(bot);
+                var low = Math.min(current, value);
+                var high = Math.max(current, value);
+                q.addLast(new Pair<>(low, lowSinks.get(bot)));
+                q.addLast(new Pair<>(high, highSinks.get(bot)));
+            }
+            return paths;
+        }
+
+        private static class Pair<T1, T2> {
+            public final T1 first;
+            public final T2 second;
+
+            public Pair(T1 first, T2 second) {
+                this.first = first;
+                this.second = second;
+            }
+
+            @Override
+            public boolean equals(Object o) {
+                if (this == o) return true;
+                if (o == null || getClass() != o.getClass()) return false;
+                Pair<?, ?> pair = (Pair<?, ?>) o;
+                return first.equals(pair.first) &&
+                        second.equals(pair.second);
+            }
+
+            @Override
+            public int hashCode() {
+                return Objects.hash(first, second);
+            }
+        }
+    }
+
+    private static class Sink {
+        public final int target;
+        public final boolean isOutput;
+
+        public Sink(int target, boolean isOutput) {
+            this.target = target;
+            this.isOutput = isOutput;
+        }
+    }
 }

java/src/test/java/com/github/saser/adventofcode/year2016/day10/Day10Test.java

@@ -10,7 +10,7 @@ public class Day10Test {
     @Test
     public void part1Actual() throws IOException {
         try (var input = new FileReader("inputs/2016/10")) {
-            var output = "";
+            var output = "118";
             var result = Day10.part1(input);
             Assert.assertEquals("no error", "", result.error);
             Assert.assertEquals("correct output", output, result.answer);