Part 1 fun calc(input: String): BigInteger { val (files,spaces) = input.windowed(2, 2, true) { it[0].digitToInt() to (it.getOrNull(1)?.digitToInt() ?: 0) }.unzip() val rev = sequence { files.mapIndexed { i, c -> i to c }.reversed().forEach { p -> repeat(p.second) { yield(p.first) } } }.iterator() return files.mapIndexed { i, c -> i to c }.zip(spaces).flatMap { p -> List(p.first.second) { p.first.first } + List(p.second) { rev.next() } } .mapIndexed { i, c -> (i * c).toBigInteger() }.take(files.sum()).fold(BigInteger.ZERO){a,b->a+b} }
I had a lot of fun with this one (even though the time I had to work on it was really broken up over the course of yesterday and this morning). For Part B, I did merge empty spaces together. I felt it made it easier to find the place to put the file. I count backwards from the highest file ID, and look for the first empty space that's big enough to hold the file: val fileToMove = this.blockMap.firstOrNull() { it.fileId == fileIdx } ?: continue val fileToMoveIdx = this.blockMap.indexOf(fileToMove) val firstFreeBlockIndex = this.blockMap.indexOfFirst { it.blockType == BlockType.FREE && it.blockSize >= fileToMove.blockSize } If the firstFreeBlock is AFTER the file we're moving, OR there is no free block big enough, then leave the file where it is and continue with the next file ID Then: - replace the file in the list with a free space block of the same size - insert the file before firstFreeBlock - shrink the size of firstFreeBlock - if firstFreeBlock is size 0 then remove it from the list this.blockMap[fileToMoveIdx] = DiskBlock(-1, fileToMove.blockSize, BlockType.FREE) this.blockMap.add(firstFreeBlockIndex, fileToMove) firstFreeBlock.blockSize -= fileToMove.blockSize if (firstFreeBlock.blockSize == 0) { this.blockMap.remove(firstFreeBlock) } And then compact (or I guess "coalesce" is the proper term) the free space blocks And then move on to the next file As an aside, I haven't needed to use BigInteger, except for some exceptional circumstances in previous years. Almost always the solutions have fit just fine in Longs.
Part 1
fun calc(input: String): BigInteger {
val (files,spaces) = input.windowed(2, 2, true) { it[0].digitToInt() to (it.getOrNull(1)?.digitToInt() ?: 0) }.unzip()
val rev = sequence { files.mapIndexed { i, c -> i to c }.reversed().forEach { p -> repeat(p.second) { yield(p.first) } } }.iterator()
return files.mapIndexed { i, c -> i to c }.zip(spaces).flatMap { p -> List(p.first.second) { p.first.first } + List(p.second) { rev.next() } }
.mapIndexed { i, c -> (i * c).toBigInteger() }.take(files.sum()).fold(BigInteger.ZERO){a,b->a+b} }
I had a lot of fun with this one (even though the time I had to work on it was really broken up over the course of yesterday and this morning). For Part B, I did merge empty spaces together. I felt it made it easier to find the place to put the file. I count backwards from the highest file ID, and look for the first empty space that's big enough to hold the file:
val fileToMove = this.blockMap.firstOrNull() { it.fileId == fileIdx } ?: continue
val fileToMoveIdx = this.blockMap.indexOf(fileToMove)
val firstFreeBlockIndex = this.blockMap.indexOfFirst { it.blockType == BlockType.FREE && it.blockSize >= fileToMove.blockSize }
If the firstFreeBlock is AFTER the file we're moving, OR there is no free block big enough, then leave the file where it is and continue with the next file ID
Then:
- replace the file in the list with a free space block of the same size
- insert the file before firstFreeBlock
- shrink the size of firstFreeBlock
- if firstFreeBlock is size 0 then remove it from the list
this.blockMap[fileToMoveIdx] = DiskBlock(-1, fileToMove.blockSize, BlockType.FREE)
this.blockMap.add(firstFreeBlockIndex, fileToMove)
firstFreeBlock.blockSize -= fileToMove.blockSize
if (firstFreeBlock.blockSize == 0) {
this.blockMap.remove(firstFreeBlock)
}
And then compact (or I guess "coalesce" is the proper term) the free space blocks
And then move on to the next file
As an aside, I haven't needed to use BigInteger, except for some exceptional circumstances in previous years. Almost always the solutions have fit just fine in Longs.
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