java/2016/20: add solution for part 2

Author: saser

java/src/main/java/com/github/saser/adventofcode/year2016/day20/Day20.java

@@ -2,6 +2,7 @@
 
 import java.io.BufferedReader;
 import java.io.Reader;
+import java.util.ArrayList;
 import java.util.Comparator;
 import java.util.List;
 import java.util.stream.Collectors;
@@ -21,8 +22,15 @@ public static Result part2(Reader r) {
 
     private static Result solve(Reader r, int part) {
         var intervals = parse(r);
-        var answer = firstAvailable(intervals);
-        return Result.ok(Long.toString(answer));
+        var available = toAvailable(intervals);
+        if (part == 1) {
+            var first = available.get(0);
+            return Result.ok(Long.toString(first.v1));
+        }
+        var sum = available.stream()
+                .mapToLong(interval -> interval.v2 - interval.v1)
+                .sum();
+        return Result.ok(Long.toString(sum));
     }
 
     private static List<Tuple2<Long, Long>> parse(Reader r) {
@@ -37,31 +45,34 @@ private static List<Tuple2<Long, Long>> parse(Reader r) {
                 .collect(Collectors.toUnmodifiableList());
     }
 
-    private static long firstAvailable(List<Tuple2<Long, Long>> intervals) {
-        var sorted = intervals.stream()
-                .flatMap(tuple -> {
-                    var start = tuple.v1;
-                    var end = tuple.v2;
-                    return Stream.of(new Tuple2<>(start, false), new Tuple2<>(end + 1, true));
-                })
-                .sorted(Comparator.<Tuple2<Long, Boolean>, Long>comparing(tuple -> tuple.v1)
-                        .thenComparing(tuple -> tuple.v2));
+    private static List<Tuple2<Long, Long>> toAvailable(List<Tuple2<Long, Long>> blocked) {
+        var sorted = blocked.stream()
+                .flatMap(interval -> Stream.of(new Tuple2<>(interval.v1, false), new Tuple2<>(interval.v2 + 1, true)))
+                .sorted(Comparator.<Tuple2<Long, Boolean>, Long>comparing(edge -> edge.v1)
+                        .thenComparing(edge -> edge.v2));
         var it = sorted.iterator();
-        if (it.next().v1 > 0) {
-            return 0;
-        }
-        var depth = 1;
+        var available = new ArrayList<Tuple2<Long, Long>>();
+        long start = 0;
+        var depth = 0;
         while (it.hasNext()) {
-            var element = it.next();
-            if (element.v2) {
+            var edge = it.next();
+            var value = edge.v1;
+            var isEnd = edge.v2;
+            if (isEnd) {
                 depth--;
                 if (depth == 0) {
-                    return element.v1;
+                    start = value;
                 }
             } else {
                 depth++;
+                if (depth == 1) {
+                    available.add(new Tuple2<>(start, value));
+                }
             }
         }
-        return -1;
+        available.add(new Tuple2<>(start, (1L << 32) - 1));
+        return available.stream()
+                .filter(interval -> interval.v2 > interval.v1)
+                .collect(Collectors.toUnmodifiableList());
     }
 }

java/src/test/java/com/github/saser/adventofcode/year2016/day20/Day20Test.java

@@ -27,22 +27,13 @@ public void part1Actual() throws IOException {
         }
     }
 
-    // @Test
-    // public void part2Example() {
-    //     var input = new StringReader("");
-    //     var output = "";
-    //     var result = Day20.part2(input);
-    //     Assert.assertEquals("no error", "", result.error);
-    //     Assert.assertEquals("correct output", output, result.answer);
-    // }
-
-    // @Test
-    // public void part2Actual() throws IOException {
-    //     try (var input = new FileReader("inputs/2016/20")) {
-    //         var output = "";
-    //         var result = Day20.part2(input);
-    //         Assert.assertEquals("no error", "", result.error);
-    //         Assert.assertEquals("correct output", output, result.answer);
-    //     }
-    // }
+     @Test
+     public void part2Actual() throws IOException {
+         try (var input = new FileReader("inputs/2016/20")) {
+             var output = "";
+             var result = Day20.part2(input);
+             Assert.assertEquals("no error", "", result.error);
+             Assert.assertEquals("correct output", output, result.answer);
+         }
+     }
 }