From 03f0d06f300fe70de069bbfd471c0f90804a9c16 Mon Sep 17 00:00:00 2001
From: Christopher Bohn <bohn@unl.edu>
Date: Wed, 7 Dec 2022 14:42:00 -0600
Subject: [PATCH] Completed Year 2022 Day 7
---
2022/README.md | 12 +++++++-
.../java/edu/unl/cse/bohn/year2022/Day7.java | 28 +++++++++++++------
2 files changed, 31 insertions(+), 9 deletions(-)
diff --git a/2022/README.md b/2022/README.md
index 80c889b..de75d51 100644
--- a/2022/README.md
+++ b/2022/README.md
@@ -204,7 +204,17 @@ It looks like the puzzle input has fewer than 200 directories. YOLO. So, add to
### Part 2
-...
+The new subproblems are
+- Determine how much space needs to be freed
+- Find the smallest directory whose size is greater than that amount
+
+### Refactoring
+
+In Part 1, we looked for all directories *below* some threshold size.
+In Part 2 we want the smallest directory *above* some threshold size, which can be obtained by looking for all
+directories larger than the threshold and selecting the smallest.
+By parameterizing the searching method with the threshold size and whether we're looking above or below the threshold,
+it will serve both parts.
## Day 8
diff --git a/2022/src/main/java/edu/unl/cse/bohn/year2022/Day7.java b/2022/src/main/java/edu/unl/cse/bohn/year2022/Day7.java
index 52404cb..2036ed8 100644
--- a/2022/src/main/java/edu/unl/cse/bohn/year2022/Day7.java
+++ b/2022/src/main/java/edu/unl/cse/bohn/year2022/Day7.java
@@ -36,13 +36,16 @@ public class Day7 extends Puzzle {
Directory rootDirectory = null;
public static final long THRESHOLD_DIRECTORY_SIZE = 100000;
+ public static final long TOTAL_FILESYSTEM_SIZE = 70000000;
+ public static final long SPACE_REQUIRED = 30000000;
@Override
public long computePart1(List<String> data) {
if (rootDirectory == null) {
rootDirectory = buildDirectoryTree(data);
}
- Set<Directory> directoriesBelowThreshold = getSmallDirectories(rootDirectory);
+ Set<Directory> directoriesBelowThreshold
+ = getDirectoriesAboveOrBelowThreshold(rootDirectory, THRESHOLD_DIRECTORY_SIZE, true);
return directoriesBelowThreshold.stream().mapToLong(Directory::getSize).sum();
}
@@ -51,7 +54,11 @@ public class Day7 extends Puzzle {
if (rootDirectory == null) {
rootDirectory = buildDirectoryTree(data);
}
- return 0;
+ long currentlyUnusedSpace = TOTAL_FILESYSTEM_SIZE - rootDirectory.getSize();
+ long spaceNeededToBeFreed = SPACE_REQUIRED - currentlyUnusedSpace;
+ Set<Directory> directoriesAboveThreshold
+ = getDirectoriesAboveOrBelowThreshold(rootDirectory, spaceNeededToBeFreed, false);
+ return directoriesAboveThreshold.stream().mapToLong(Directory::getSize).min().orElse(Long.MAX_VALUE);
}
private Directory buildDirectoryTree(List<String> data) {
@@ -85,15 +92,20 @@ public class Day7 extends Puzzle {
return root;
}
- private Set<Directory> getSmallDirectories(Directory rootOfSubtree) {
- Set<Directory> smallDirectories = new HashSet<>();
- if (rootOfSubtree.getSize() <= THRESHOLD_DIRECTORY_SIZE) {
- smallDirectories.add(rootOfSubtree);
+ private Set<Directory> getDirectoriesAboveOrBelowThreshold(Directory rootOfSubtree,
+ long threshold,
+ boolean lookBelowThreshold) {
+ Set<Directory> matches = new HashSet<>();
+ if (lookBelowThreshold && rootOfSubtree.getSize() <= threshold) {
+ matches.add(rootOfSubtree);
+ }
+ if (!lookBelowThreshold && rootOfSubtree.getSize() >= threshold) {
+ matches.add(rootOfSubtree);
}
for (Directory subdirectory : rootOfSubtree.getSubdirectories()) {
- smallDirectories.addAll(getSmallDirectories(subdirectory));
+ matches.addAll(getDirectoriesAboveOrBelowThreshold(subdirectory, threshold, lookBelowThreshold));
}
- return smallDirectories;
+ return matches;
}
private static class Directory {
--
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