Advent-of-Code-2022/7/solution.mjs

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}`
);