Day 7

7/solution.mjs

@@ -0,0 +1,120 @@
+import { readFileSync } from 'node:fs';
+
+const input = readFileSync('input', 'utf-8');
+
+class Directory {
+  constructor(parent, name) {
+    this.parent = parent;
+    this.name = name;
+    this.contents = [];
+  }
+
+  getOrCreateSubdirectory(name) {
+    let dir = this.contents.find(c => c.name === name);
+    if (dir) {
+      return dir;
+    }
+    dir = new Directory(this, name);
+    this.contents.push(dir);
+    return dir;
+  }
+
+  getSize() {
+    return this.contents.reduce((size, entry) => {
+      if (entry instanceof File) {
+        return size + entry.size;
+      } else {
+        return size + entry.getSize();
+      }
+    }, 0);
+  }
+
+  getRecursiveSubdirs() {
+    const subdirs = [];
+
+    for (const entry of this.contents) {
+      if (entry instanceof Directory) {
+        subdirs.push(entry);
+        subdirs.push(...entry.getRecursiveSubdirs());
+      }
+    }
+
+    return subdirs;
+  }
+}
+
+class File {
+  constructor(parent, name, size) {
+    this.parent = parent;
+    this.name = name;
+    this.size = size;
+  }
+}
+
+
+let currentDirectory;
+let rootDirectory;
+
+for (const line of input.split('\n').filter(line => line)) {
+  if (line.startsWith('$ ls')) {
+    // ignore
+  } else if (line.startsWith('$ cd')) {
+    const path = line.slice(5).trim();
+
+    if (path === '..') {
+      currentDirectory = currentDirectory.parent;
+    } else {
+      if (!currentDirectory) {
+        currentDirectory = new Directory(null, path);
+        rootDirectory = currentDirectory;
+      } else {
+        currentDirectory = currentDirectory.getOrCreateSubdirectory(path);
+      }
+    }
+  } else {
+    if (line.startsWith('dir')) {
+      const path = line.slice(4).trim();
+      currentDirectory.getOrCreateSubdirectory(path);
+    } else {
+      let [size, name] = line.split(' ', 2);
+      size = parseInt(size);
+      const file = new File(currentDirectory, name, size);
+      currentDirectory.contents.push(file);
+    }
+  }
+}
+
+// Sum of directories with size less than or equal to 100000
+let totalSizeOfMatchingDirs = 0;
+
+for (const dir of rootDirectory.getRecursiveSubdirs()) {
+  const size = dir.getSize();
+  if (size <= 100000) {
+    totalSizeOfMatchingDirs += size;
+  }
+}
+
+console.log(`Sum of directory sizes under 100000: ${totalSizeOfMatchingDirs}`);
+
+
+const totalDiskSpace = 70000000;
+const spaceNeeded = 30000000;
+const totalUsedSpace = rootDirectory.getSize();
+
+const totalUnusedSpace = totalDiskSpace - totalUsedSpace;
+
+const spaceToFree = spaceNeeded - totalUnusedSpace;
+
+let sizeOfDirToDelete = rootDirectory.getSize();
+for (const dir of rootDirectory.getRecursiveSubdirs()) {
+  const size = dir.getSize();
+
+  if (size >= spaceToFree) {
+    sizeOfDirToDelete = Math.min(sizeOfDirToDelete, size);
+  }
+}
+
+console.log(
+  `Delete directory of size ${sizeOfDirToDelete} to free ${spaceToFree}`
+);
+