Day 9

2024/09/index2.ts

@@ -0,0 +1,71 @@
+const fs = require('fs');
+
+const input = fs.readFileSync(__dirname + '/input.txt', 'utf8');
+
+interface MyFile { id: number, addr: number, size: number };
+
+const files: Array<MyFile> = [];
+
+let pointer = 0;
+let id = 0;
+
+for (let i = 0; i < input.length; i++) {
+    const size = parseInt(input[i]);
+    if (i % 2 === 0) {
+        files.push({ id, size, addr: pointer });
+        id++;
+    }
+    pointer += size;
+}
+
+function printDisk() {
+    const disk: Array<string> = [];
+    files.forEach((file) => {
+        for (let i = file.addr; i < file.addr + file.size; i++) {
+            disk[i] = ''+file.id;
+        }
+    });
+
+    let diskStr = '';
+    for (let i = 0; i < disk.length; i++) {
+        diskStr += disk[i] || '.';
+    }
+    console.log(diskStr);
+}
+
+function getFirstSpace(size: number): null|{ addr: number, size: number, index: number } {
+    for (let i = 0; i < files.length; i++) {
+        const file = files[i];
+        const nextFile = files[i+1];
+        if (file && nextFile) {
+            const fileEnd = file.addr + file.size;
+            if (nextFile.addr - fileEnd >= size) {
+                return {
+                    addr: fileEnd,
+                    size: nextFile.addr - fileEnd,
+                    index: i + 1,
+                };
+            }
+        }
+    }
+    return null;
+}
+
+files.slice().reverse().forEach((lastFile, i) => {
+    const firstFreeSpace = getFirstSpace(lastFile.size);
+    if (!firstFreeSpace || firstFreeSpace.addr >= lastFile.addr) {
+        return;
+    }
+    files.splice(files.indexOf(lastFile), 1);
+    files.splice(firstFreeSpace.index, 0, { addr: firstFreeSpace.addr, id: lastFile.id, size: lastFile.size });
+});
+
+let checksum = 0;
+
+files.forEach((file) => {
+    for (let i = file.addr; i < file.addr + file.size; i++) {
+        checksum += i * file.id;
+    }
+});
+
+console.log(checksum);