7.2 was easier, at least

2022/7/index2.js

@@ -0,0 +1,75 @@
+
+const fs = require('fs/promises');
+
+const createNode = (parent) => {
+  return {
+    parent,
+    children: {},
+    localSize: 0
+  };
+};
+
+let answer = 0;
+
+(async () => {
+  const input = await fs.readFile("./input.txt", 'utf8');
+
+  const lines = input.split("\n");
+
+  const files = createNode();
+
+  lines.reduce((node, line) => {
+    const cd = line.match(/^\$ cd (.*)$/);
+    if(cd) {
+      if(cd[1] == "..") {
+        return node.parent;
+      }
+      return node.children[cd[1]];
+    }
+    const dir = line.match(/^dir (.*)$/);
+    if(dir) {
+      node.children[dir[1]] = createNode(node);
+    }
+    const file = line.match(/^(\d+) .*$/);
+    if(file) {
+      node.localSize += parseFloat(file[1]);
+    }
+
+    return node;
+
+  }, files);
+
+
+  const fullSize = totalSmallerDirs(files);
+
+  console.log("FULL SIZE: ", fullSize);
+
+  console.log("SPACE NEEDED: ",  fullSize - 40000000);
+
+  const [_, bestDeletionCandidate] = findBestDeletionCandidate(files, fullSize - 40000000);
+  console.log("Best candidate for deletion is of size: ", bestDeletionCandidate);
+})();
+
+const totalSmallerDirs = (node) => {
+  let totalSize =  node.localSize;
+
+  totalSize += sum(Object.values(node.children).map(totalSmallerDirs));
+
+  if(totalSize <= 100000) {
+    answer += totalSize;
+  }
+  return totalSize;
+}
+
+const findBestDeletionCandidate = (node, spaceNeeded) => {
+  let totalSize =  node.localSize;
+
+  const childrenResults = Object.values(node.children).map(child => findBestDeletionCandidate(child, spaceNeeded));
+  totalSize += sum(childrenResults.map(([x]) => x));
+  const deletionCandidates = childrenResults.map(([_, y]) => y);
+  deletionCandidates.push(totalSize);
+  console.log("Deletion Candidates: ", deletionCandidates);
+
+  return [totalSize, deletionCandidates.reduce((best, current) => current < best && current >= spaceNeeded ? current : best, Infinity)];
+}
+const sum = (arr) => arr.reduce((total, num) => total+num, 0);