Day 9

2024/09/index.ts

@@ -4,9 +4,7 @@ const input = fs.readFileSync(__dirname + '/input.txt', 'utf8');
 
 interface MyFile { id: number, addr: number, size: number };
 
-const freeSpaces: Array<{ addr: number, size: number }> = [];
 const files: Array<MyFile> = [];
-const reorderedFiles: Array<MyFile> = [];
 
 let pointer = 0;
 let id = 0;
@@ -16,18 +14,10 @@ for (let i = 0; i < input.length; i++) {
     if (i % 2 === 0) {
         files.push({ id, size, addr: pointer });
         id++;
-    } else if (size) {
-        freeSpaces.push({ addr: pointer, size });
     }
     pointer += size;
 }
 
-const finalSpace = { addr: pointer, size: 0 };
-
-if (input.length % 2 !== 0) {
-    freeSpaces.push(finalSpace);
-}
-
 function printDisk() {
     const disk: Array<string> = [];
     files.forEach((file) => {
@@ -35,28 +25,48 @@ function printDisk() {
             disk[i] = ''+file.id;
         }
     });
-    reorderedFiles.forEach((file) => {
-        for (let i = file.addr; i < file.addr + file.size; i++) {
-            disk[i] = ''+file.id;
-        }
-    });
-    freeSpaces.forEach((space) => {
-        for (let i = space.addr; i < space.addr + space.size; i++) {
-            disk[i] = '.';
-        }
-    });
 
-    console.log(disk.join(''));
+    let diskStr = '';
+    for (let i = 0; i < disk.length; i++) {
+        diskStr += disk[i] || '.';
+    }
+    console.log(diskStr);
+}
+
+function getFirstSpace(): 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) {
+                return {
+                    addr: fileEnd,
+                    size: nextFile.addr - fileEnd,
+                    index: i + 1,
+                };
+            }
+        }
+    }
+    return null;
 }
-console.log(files);
 
 
+top:
 while (true) {
     const lastFile = files.pop()!;
     let remainingSize = lastFile.size;
-    console.log(files, lastFile, freeSpaces);
     while (remainingSize > 0) {
-        const firstFreeSpace = freeSpaces.shift()!;
+        const firstFreeSpace = getFirstSpace();
+        if (!firstFreeSpace || firstFreeSpace.addr >= lastFile.addr) {
+            const secondLastFile = files[files.length - 1];
+            files.push({
+                addr: secondLastFile.addr + secondLastFile.size,
+                size: remainingSize,
+                id: lastFile.id,
+            });
+            break top;
+        }
         let filePartSize;
         let remainingFreeSpace;
         if (remainingSize < firstFreeSpace.size) {
@@ -66,38 +76,17 @@ while (true) {
             filePartSize = firstFreeSpace.size;
             remainingFreeSpace = 0;
         }
-        reorderedFiles.push({ addr: firstFreeSpace.addr, id: lastFile.id, size: filePartSize });
-        finalSpace.size += filePartSize;
-        finalSpace.addr -= filePartSize;
+        files.splice(firstFreeSpace.index, 0, { addr: firstFreeSpace.addr, id: lastFile.id, size: filePartSize });
         remainingSize -= filePartSize;
-        if (remainingFreeSpace) {
-            freeSpaces.unshift({ addr: firstFreeSpace.addr + filePartSize, size: remainingFreeSpace });
-        }
-    }
-
-    let i = freeSpaces.length - 2;
-    if (!freeSpaces[i]) {
-        break;
-    }
-    while (freeSpaces[i].addr + freeSpaces[i].size === finalSpace.addr) {
-        finalSpace.addr = freeSpaces[i].addr;
-        finalSpace.size += freeSpaces[i].size;
-        freeSpaces[i] = finalSpace;
-        freeSpaces.pop();
-        i--;
     }
 }
 
 let checksum = 0;
 
-const allFiles = files.concat(reorderedFiles);
-allFiles.sort((a, b) => a.addr - b.addr);
-console.log(allFiles, freeSpaces);
-
-allFiles.forEach((file) => {
+files.forEach((file) => {
     for (let i = file.addr; i < file.addr + file.size; i++) {
         checksum += i * file.id;
     }
 });
 
-console.log(checksum);
+console.log(checksum);