java/2016/22: add solution for part 1

Author: saser

java/src/main/java/com/github/saser/adventofcode/year2016/day22/BUILD.bazel

@@ -3,5 +3,8 @@ package(default_visibility = ["//visibility:public"])
 java_library(
     name = "day22",
     srcs = glob(["*.java"]),
-    deps = ["//java/src/main/java/com/github/saser/adventofcode:adventofcode"],
+    deps = [
+        "//java/src/main/java/com/github/saser/adventofcode/geo:geo",
+        "//java/src/main/java/com/github/saser/adventofcode:adventofcode",
+    ],
 )

java/src/main/java/com/github/saser/adventofcode/year2016/day22/Day22.java

@@ -1,9 +1,15 @@
 package com.github.saser.adventofcode.year2016.day22;
 
+import java.io.BufferedReader;
 import java.io.Reader;
-import java.util.stream.Stream;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Set;
+import java.util.regex.Pattern;
+import java.util.stream.Collectors;
 
 import com.github.saser.adventofcode.Result;
+import com.github.saser.adventofcode.geo.Point2D;
 
 public final class Day22 {
     public static Result part1(Reader r) {
@@ -15,6 +21,81 @@ public static Result part2(Reader r) {
     }
 
     private static Result solve(Reader r, int part) {
-        return Result.err("not implemented yet");
+        var grid = Grid.parse(r);
+        var count = grid.findViable().size();
+        return Result.ok(Integer.toString(count));
+    }
+
+    private static class Node {
+        public final int used;
+        public final int available;
+
+        public Node(int used, int available) {
+            this.used = used;
+            this.available = available;
+        }
+
+        public static boolean viable(Node a, Node b) {
+            if (a.used == 0) {
+                return false;
+            }
+            return a.used <= b.available;
+        }
+    }
+
+    private static class Grid {
+        public final Map<Point2D, Node> nodes;
+
+        public Grid(Map<Point2D, Node> nodes) {
+            this.nodes = nodes;
+        }
+
+        public static Grid parse(Reader r) {
+            var re = Pattern.compile("/dev/grid/node-x(\\d+)-y(\\d+)\\s+(\\d+)T\\s+(\\d+)T\\s+(\\d+)T\\s+(\\d+)%");
+            var nodes = new HashMap<Point2D, Node>();
+            var maxX = 0;
+            var maxY = 0;
+            var it = new BufferedReader(r)
+                    .lines()
+                    .iterator();
+            while (it.hasNext()) {
+                var line = it.next();
+                var matcher = re.matcher(line);
+                if (!matcher.matches()) {
+                    continue;
+                }
+                var x = Integer.parseInt(matcher.group(1));
+                maxX = Math.max(maxX, x);
+                var y = Integer.parseInt(matcher.group(2));
+                maxY = Math.max(maxY, y);
+                var point = new Point2D(x, y);
+                var used = Integer.parseInt(matcher.group(4));
+                var available = Integer.parseInt(matcher.group(5));
+                nodes.put(point, new Node(used, available));
+            }
+            return new Grid(nodes);
+        }
+
+        private Point2D findEmpty() {
+            return this.nodes
+                    .entrySet()
+                    .stream()
+                    .filter(entry -> entry.getValue().used == 0)
+                    .map(Map.Entry::getKey)
+                    .findFirst()
+                    .get();
+        }
+
+        public Set<Point2D> findViable() {
+            var empty = this.findEmpty();
+            var emptyNode = this.nodes.get(empty);
+            return this.nodes
+                    .entrySet()
+                    .stream()
+                    .filter(entry -> !entry.getKey().equals(empty))
+                    .filter(entry -> Node.viable(entry.getValue(), emptyNode))
+                    .map(Map.Entry::getKey)
+                    .collect(Collectors.toSet());
+        }
     }
 }

java/src/test/java/com/github/saser/adventofcode/year2016/day22/Day22Test.java

@@ -10,7 +10,7 @@ public class Day22Test {
     @Test
     public void part1Actual() throws IOException {
         try (var input = new FileReader("inputs/2016/22")) {
-            var output = "";
+            var output = "888";
             var result = Day22.part1(input);
             Assert.assertEquals("no error", "", result.error);
             Assert.assertEquals("correct output", output, result.answer);