Day 9 part 1 and partial part 2
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using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Reflection.Emit;
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using System.Text;
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using System.Threading.Tasks;
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using System.Text.RegularExpressions;
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using System.ComponentModel;
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using System.Data;
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namespace Advent24
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{
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internal class Day9
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{
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public Day9()
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{
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String fileData = System.IO.File.ReadAllText(@"..\..\..\inputd9.txt");
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Int128 checksumWholeFile = 0;
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Int64 checksum = 0;
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Int32 leftDigitInt;
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Int32 rightDigitInt;
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Int64 i = 0; // left-most iterator in expanded sequence
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Int32 leftFileID = 0;
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// 1 will be subtracted on first iteration, to make this (fileData.Length-1)/2
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Int32 rightFileID = (fileData.Length+1)/2;
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// j = right-most position in compressed sequence; 1 will be subtracted on first iteration, to make this fileData.Length-1
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Int32 j = fileData.Length;
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Int32 leftBlockLength;
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Int32 rightBlockLength = 0;
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Boolean leftIsFileBlock = true;
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Boolean rightIsFileBlock = (fileData.Length % 2) == 1;
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foreach(Char digitChar in fileData)
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{
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// The .toString() is needed to convert '2' to "2" to get 2 from .ToInt32(), otherwise we get the
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// ASCII value of '2' (when we just wanted the number 2) when converting a Char ('2') to Int32.
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leftDigitInt = System.Convert.ToInt32(digitChar.ToString());
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if (leftIsFileBlock)
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{
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leftBlockLength = leftDigitInt;
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// part of the same file block was handled from the right end,
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// so only the remaining length of that block is to be handled by
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// from the left end
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if (leftFileID == rightFileID)
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{
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leftBlockLength = rightBlockLength;
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}
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// fileID * Sum(A_n from i to i+n-1)
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checksum += leftFileID * (leftBlockLength * (2*i + leftBlockLength - 1) / 2);
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//for (int l = 0; l < leftBlockLength; l++)
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// Console.Write("{0:d},", leftFileID);
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i += leftBlockLength;
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leftFileID += 1;
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// immediately after handling the leftFileID == rightFileID case, we should exit the
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// loop after having incremented leftFileID above, because it has already been fully
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// handled from the right end - and thus has already been incorporated in the checksum.
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if (leftFileID > rightFileID)
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{
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// to remove trailing comma
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//Console.Write("\b ");
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break;
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}
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}
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else
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{
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// left is free block
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leftBlockLength = leftDigitInt;
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if (rightBlockLength < 0)
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throw new ApplicationException(nameof(rightBlockLength)+" must be >= 0 but was "+rightBlockLength.ToString());
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if (rightBlockLength == 0)
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{
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j -= 1;
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rightIsFileBlock = !rightIsFileBlock;
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rightDigitInt = System.Convert.ToInt32(fileData[j].ToString());
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rightFileID -= 1;
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rightBlockLength = rightDigitInt;
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}
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//Console.Write("\b[");
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while (leftBlockLength >= rightBlockLength)
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{
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checksum += rightFileID * (rightBlockLength * (2 * i + rightBlockLength - 1) / 2);
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i += rightBlockLength;
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//for (int l = 0; l < rightBlockLength; l++)
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// Console.Write("{0:d},", rightFileID);
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leftBlockLength -= rightBlockLength;
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// right-ended free block
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j -= 1;
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rightIsFileBlock = !rightIsFileBlock;
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rightDigitInt = System.Convert.ToInt32(fileData[j].ToString());
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// moving leftward from the right-ended free block, so handling a file block
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j -= 1;
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rightIsFileBlock = !rightIsFileBlock;
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rightDigitInt = System.Convert.ToInt32(fileData[j].ToString());
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rightFileID -= 1;
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// if there are more empty spaces left (leftBlockLength) in the free block handled
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// from the left side but no more right handled file blocks to move there (if
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// rightFileID > leftFileID), we've reached the end of the checksum calculation and
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// should exit the loop without adding anything further to the checksum
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if (leftFileID > rightFileID)
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break;
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rightBlockLength = rightDigitInt;
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}
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// if we broke from the inner 'for' loop above because leftFileID > rightFileID, we should break
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// out of the outer 'foreach' loop too, for the same reason
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if (leftFileID > rightFileID)
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{
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//Console.Write("\b]");
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break;
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}
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if (leftBlockLength > 0)
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{
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// Also, leftBlockLength < rightBlockLength after the above while() loop
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checksum += rightFileID * (leftBlockLength * (2 * i + leftBlockLength - 1) / 2);
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i += leftBlockLength;
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//for (int l = 0; l < leftBlockLength; l++)
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// Console.Write("{0:d},", rightFileID);
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rightBlockLength -= leftBlockLength;
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}
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else
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//Console.Write(","); // to prevent opening [ from being eaten by the \b on the next line
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//Console.Write("\b]");
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;
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}
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leftIsFileBlock = !leftIsFileBlock;
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}
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//Console.WriteLine();
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Console.WriteLine("checksum = {0:d}", checksum);
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// part 2
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{
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// Linked list of tuples of (fileID, fileLength) tuples, with fileID = -1 for free lengths
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LinkedList<(Int32, Int32)> expandedDisk = new();
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Int32 digitInt;
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Int32 previousFileID = -2;
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Int32 fileID = 0;
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Int32 fileLength = 0;
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Boolean isFileBlock = true;
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// create expanded disk from disk map
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foreach(Char digitChar in fileData)
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{
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digitInt = System.Convert.ToInt32(digitChar.ToString());
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if (isFileBlock)
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{
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expandedDisk.AddLast((fileID, digitInt));
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for (Int32 ii = 0; ii < digitInt; ii++)
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Console.Write("{0:d},", fileID);
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fileID++;
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}
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else
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{
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for (Int32 ii = 0; ii < digitInt; ii++)
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Console.Write('.');
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expandedDisk.AddLast((-1, digitInt));
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}
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isFileBlock = !isFileBlock;
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}
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Console.WriteLine();
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for (LinkedListNode<(Int32, Int32)>? node = expandedDisk.Last; node != null; node = node.Previous)
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{
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fileLength = node.Value.Item2;
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fileID = node.Value.Item1;
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if (fileID == -1) // node is not free space
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continue;
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// previousFileId is no longer the negative sentinel value
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// and we've finished progressing down the fileIDs in descending order
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// and have hit up against a previously moved fileID
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if (previousFileID >= 0 && previousFileID < fileID)
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{
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//Console.WriteLine("previousFileID = {0:d}, fileID = {1:d}", previousFileID, fileID);
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previousFileID = fileID;
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continue;
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}
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for (LinkedListNode<(Int32, Int32)>? innerNode = expandedDisk.First; innerNode != node && innerNode != null; innerNode = innerNode.Next)
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{
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Int32 freeID = innerNode.Value.Item1;
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Int32 freeLength = innerNode.Value.Item2;
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//for (Int32 ii = 0; ii < freeLength; ii++)
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// if (freeID == -1)
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// Console.Write('.');
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// else
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// Console.Write("{0:d},", freeID);
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if (freeID != -1) // node is not free space
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continue;
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if (fileLength <= freeLength)
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{
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// moving file to formerly free space
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expandedDisk.AddBefore(innerNode, (fileID, fileLength));
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// changing original node to free space
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node.ValueRef = (-1, fileLength);
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// reducing or deleting free space
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if (freeLength - fileLength == 0)
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expandedDisk.Remove(innerNode);
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else
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innerNode.ValueRef = (-1, freeLength - fileLength); // fileID of free space is -1
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break;
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}
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}
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//Console.WriteLine();
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previousFileID = fileID;
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}
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//Console.WriteLine();
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Int32 blockPosition = 0;
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foreach(var fileBlockTuple in expandedDisk)
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{
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fileID = fileBlockTuple.Item1;
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fileLength = fileBlockTuple.Item2;
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// skip free blocks
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if (fileID == -1)
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{
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for (Int32 ii = 0; ii < fileLength; ii++)
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Console.Write('.');
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blockPosition += fileLength;
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continue;
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}
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checksumWholeFile += fileID * (fileLength * (2 * blockPosition + fileLength - 1) / 2);
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//Console.WriteLine("\n(intermediate) fileID = {0:d}, blockPosition = {1:d}, fileLength = {2:d}",
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// fileID, blockPosition, fileLength);
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//Console.WriteLine("(intermediate) checksumWholeFile = {0:d}", checksumWholeFile);
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for (Int32 ii = 0; ii < fileLength; ii++)
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Console.Write("{0:d},", fileID);
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blockPosition += fileLength;
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}
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}
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Console.WriteLine();
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Console.WriteLine("checksumWholeFile = {0:d}", checksumWholeFile);
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// to keep the console window from closing
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Console.ReadKey();
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}
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}
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}
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@ -14,7 +14,8 @@ namespace Advent24
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//_ = new Day5();
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//_ = new Day6();
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//_ = new Day7();
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_ = new Day8();
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//_ = new Day8();
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_ = new Day9();
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}
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}
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}
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File diff suppressed because one or more lines are too long
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@ -0,0 +1 @@
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2333133121414131402
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