private static void ParseBotInstruction(ref SpanReader parser, out int bot, out bool isLowBot, out int low, out bool isHighBot, out int high)
{
parser.SkipLength("bot ".Length);
bot = parser.ReadPosIntUntil(' ');
parser.SkipLength("gives low to ".Length);
isLowBot = parser.Peek() == 'b';
parser.SkipLength(isLowBot ? "bot ".Length : "output ".Length);
low = parser.ReadPosIntUntil(' ');
parser.SkipLength("and high to ".Length);
isHighBot = parser.Peek() == 'b';
parser.SkipLength(isHighBot ? "bot ".Length : "output ".Length);
high = parser.ReadPosIntUntil('\n');
}
private static FieldsData ParseFields(ref SpanReader reader)
{
int departureFieldsIndex = 0;
int[] departureFields = new int[6];
var fieldList = new List <Field>();
int maxFieldVal = int.MinValue;
while (reader.Peek() != '\n')
{
ReadOnlySpan <byte> fieldName = reader.ReadUntil(':');
reader.SkipLength(1);
int l1 = reader.ReadPosIntUntil('-');
int r1 = reader.ReadPosIntUntil(' ');
reader.SkipLength("or ".Length);
int l2 = reader.ReadPosIntUntil('-');
int r2 = reader.ReadPosIntUntil('\n');
fieldList.Add(new Field(l1, r1, l2, r2));
if (fieldName.StartsWith(new byte[] { (byte)'d', (byte)'e' }))
{
departureFields[departureFieldsIndex++] = fieldList.Count - 1;
}
if (r2 > maxFieldVal)
{
maxFieldVal = r2;
}
}
return(new FieldsData(fieldList, departureFields, maxFieldVal));
}
private static List <byte> ParseInput(ReadOnlySpan <byte> input)
{
var materialLocations = new List <byte>();
var materials = new Dictionary <string, int>();
var reader = new SpanReader(input);
for (int floor = 1; floor < 5; floor++)
{
reader.SkipLength(floor is 1 or 3 ? "The first floor contains ".Length : "The second floor contains ".Length);
if (reader.Peek() == 'n') // nothing relevant
{
reader.SkipLength("nothing relevant.\n".Length);
continue;
}
bool isLastItem = false;
while (!isLastItem)
{
ParseItem(ref reader, out string element, out bool isGenerator, out isLastItem);
if (!materials.TryGetValue(element, out int materialIndex))
{
materialIndex = materialLocations.Count;
materials[element] = materialIndex;
materialLocations.Add(0);
}
materialLocations[materialIndex] |= (byte)(isGenerator ? floor << 4 : floor);
}
}
return(materialLocations);
}
public void Solve(ReadOnlySpan <byte> input, Solution solution)
{
int freqIndex = 0;
int freqTotal = 0;
var freqs = new List <Frequency>();
var reader = new SpanReader(input);
while (!reader.Done)
{
freqs.Add(new Frequency {
Value = freqTotal, Index = freqIndex
});
freqIndex++;
int mul = reader.Peek() == '-' ? -1 : 1;
reader.SkipLength(1);
freqTotal += mul * reader.ReadPosIntUntil('\n');
}
foreach (Frequency freq in freqs)
{
int mod = freq.Value % freqTotal;
freq.ModTotal = mod < 0 ? mod + freqTotal : mod;
}
// sort by mods first, then by value
freqs.Sort((a, b) => a.ModTotal != b.ModTotal
? a.ModTotal.CompareTo(b.ModTotal)
: a.Value.CompareTo(b.Value));
var prev = new Frequency {
ModTotal = -1
};
int minDiff = int.MaxValue;
int minIndex = int.MaxValue;
int minFreq = 0;
foreach (Frequency freq in freqs)
{
if (freq.ModTotal == prev.ModTotal)
{
int diff = freq.Value - prev.Value;
if (diff < minDiff || (diff == minDiff && prev.Index < minIndex))
{
minDiff = diff;
minIndex = prev.Index;
minFreq = freq.Value;
}
}
prev = freq;
}
solution.SubmitPart1(freqTotal);
solution.SubmitPart2(minFreq);
}
public void Solve(ReadOnlySpan <byte> input, Solution solution)
{
var reader = new SpanReader(input.TrimEnd((byte)'\n'));
int earliestTime = reader.ReadPosIntUntil('\n');
int part1Id = -1;
int part1Time = int.MaxValue;
BigInteger product = 1;
var buses = new List <(int n, int a)>();
for (int i = 0; !reader.Done; i++)
{
if (reader.Peek() == 'x')
{
reader.SkipLength("x,".Length);
continue;
}
int busId = reader.ReadPosIntUntil(',');
// Part 1
int waitTime = busId - (earliestTime % busId);
if (waitTime < part1Time)
{
part1Id = busId;
part1Time = waitTime;
}
// Part 2
product *= busId;
int remainder = (busId - i) % busId;
if (remainder < 0)
{
remainder += busId;
}
buses.Add((busId, remainder));
}
int part1 = part1Id * part1Time;
BigInteger part2 = 0;
foreach ((int n, int a) in buses)
{
BigInteger p = product / n;
part2 += a * BigInteger.ModPow(p, n - 2, n) * p;
}
part2 %= product;
solution.SubmitPart1(part1);
solution.SubmitPart2(part2);
}
public void Solve(ReadOnlySpan <byte> input, Solution solution)
{
// assume the origin is at 1 << 15, 1 << 15
const ushort xOrigin = 1 << 15;
const ushort yOrigin = 1 << 15;
// pack the x and y ushorts into a uint
uint pos = unchecked ((uint)xOrigin << 16 | yOrigin);
uint dir = Up;
var seenLocations = new HashSet <uint> {
pos
};
int distanceToFirstRepeatedLocation = -1;
var reader = new SpanReader(input.TrimEnd((byte)'\n'));
while (true)
{
dir = MakeTurn(dir, reader.Peek() == 'L');
reader.SkipLength(1);
uint distance = (uint)reader.ReadPosIntUntil(',');
if (distanceToFirstRepeatedLocation == -1)
{
for (uint i = 0; i < distance; i++)
{
pos = unchecked (pos + dir);
if (!seenLocations.Add(pos))
{
distanceToFirstRepeatedLocation = ManhattanDistance(pos);
}
}
}
else
{
pos = unchecked (pos + dir * distance);
}
if (reader.Done)
{
break;
}
reader.SkipLength(1);
}
int distanceToDestination = ManhattanDistance(pos);
solution.SubmitPart1(distanceToDestination);
solution.SubmitPart2(distanceToFirstRepeatedLocation);
private static void ParseItem(ref SpanReader reader, out string element, out bool isGenerator, out bool isLastItem)
{
isLastItem = reader[1] == 'n'; // "and a <something>"
reader.SkipLength(isLastItem ? "and a ".Length : "a ".Length);
ReadOnlySpan <byte> elementSpan = reader.ReadUntil(' ');
isGenerator = reader.Peek() == 'g';
reader.SkipUntil(isLastItem ? '\n' : ' ');
if (!isGenerator)
{
elementSpan = elementSpan.Slice(0, elementSpan.Length - "-compatible".Length);
}
element = Encoding.ASCII.GetString(elementSpan);
}
public void Solve(ReadOnlySpan <byte> input, Solution solution)
{
int lines = input.Count((byte)'\n');
var instrs = new Instruction[lines];
int i = 0;
var reader = new SpanReader(input);
while (!reader.Done)
{
byte op = reader.Peek();
reader.SkipLength("cpy ".Length);
Param arg1, arg2;
if (op is (byte)'c' or(byte) 'j')
{
arg1 = ParseParamUntil(ref reader, ' ');
arg2 = ParseParamUntil(ref reader, '\n');
}
public void Solve(ReadOnlySpan <byte> input, Solution solution)
{
bool[,] pixels = new bool[50, 6];
bool[] rowBuffer = new bool[50];
bool[] colBuffer = new bool[6];
foreach (ReadOnlySpan <byte> line in input.SplitLines())
{
if (line[1] == 'e') // rect
{
var reader = new SpanReader(line.Slice("rect ".Length));
int width = reader.ReadPosIntUntil('x');
int height = reader.ReadPosIntUntilEnd();
for (int y = 0; y < height; y++)
{
for (int x = 0; x < width; x++)
{
pixels[x, y] = true;
}
}
}
else if (line[7] == 'c') // rotate column
{
var reader = new SpanReader(line.Slice("rotate column x=".Length));
int column = reader.ReadPosIntUntil(' ');
reader.SkipLength("by ".Length);
int rotateAmount = reader.ReadPosIntUntilEnd();
for (int i = 0; i < 6; i++)
{
colBuffer[i] = pixels[column, i];
int target = i - rotateAmount;
if (target < 0)
{
target += 6;
}
// if the target has already been swapped, get it from the buffer
pixels[column, i] = target < i ? colBuffer[target] : pixels[column, target];
}
}
else // rotate row
{
var reader = new SpanReader(line.Slice("rotate row y=".Length));
int row = reader.Peek() - '0';
reader.SkipLength("0 by ".Length);
int rotateAmount = reader.ReadPosIntUntilEnd();
for (int i = 0; i < 50; i++)
{
rowBuffer[i] = pixels[i, row];
int target = i - rotateAmount;
if (target < 0)
{
target += 50;
}
// if the target has already been swapped, get it from the buffer
pixels[i, row] = target < i ? rowBuffer[target] : pixels[target, row];
}
}
}
int part1 = 0;
foreach (bool pixel in pixels)
{
if (pixel)
{
part1++;
}
}
Span <char> part2 = stackalloc char[10];
for (int i = 0; i < 10; i++)
{
int letterPixels = 0;
for (int row = 0; row < 6; row++)
{
for (int col = 0; col < 5; col++)
{
if (pixels[i * 5 + col, row])
{
letterPixels |= 1 << (29 - (row * 5 + col));
}
}
}
part2[i] = OCR.MaskToLetter(letterPixels);
}
solution.SubmitPart1(part1);
solution.SubmitPart2(part2);
}
public void Solve(ReadOnlySpan <byte> input, Solution solution)
{
// Part 1
int x1 = 0, y1 = 0;
int dx1 = 1, dy1 = 0;
// Part 2
int x2 = 0, y2 = 0;
int dx2 = 10, dy2 = 1;
var reader = new SpanReader(input);
while (!reader.Done)
{
byte dir = reader.Peek();
reader.SkipLength(1);
int amount = reader.ReadPosIntUntil('\n');
switch (dir)
{
case (byte)'N':
y1 += amount;
dy2 += amount;
break;
case (byte)'S':
y1 -= amount;
dy2 -= amount;
break;
case (byte)'E':
x1 += amount;
dx2 += amount;
break;
case (byte)'W':
x1 -= amount;
dx2 -= amount;
break;
case (byte)'L':
for (int i = amount; i > 0; i -= 90)
{
RotateLeft(ref dx1, ref dy1);
RotateLeft(ref dx2, ref dy2);
}
break;
case (byte)'R':
for (int i = amount; i > 0; i -= 90)
{
RotateRight(ref dx1, ref dy1);
RotateRight(ref dx2, ref dy2);
}
break;
case (byte)'F':
x1 += amount * dx1;
y1 += amount * dy1;
x2 += amount * dx2;
y2 += amount * dy2;
break;
}
}
int part1 = Math.Abs(x1) + Math.Abs(y1);
int part2 = Math.Abs(x2) + Math.Abs(y2);
solution.SubmitPart1(part1);
solution.SubmitPart2(part2);
}
public void Solve(ReadOnlySpan <byte> input, Solution solution)
{
var ingredientCount = new Dictionary <string, int>();
var allgerenCandidates = new Dictionary <string, HashSet <string> >();
var ingredientSet = new HashSet <string>();
var reader = new SpanReader(input);
int totalIngredients = 0;
while (!reader.Done)
{
while (reader.Peek() != '(')
{
string ingredient = Encoding.ASCII.GetString(reader.ReadUntil(' '));
ingredientCount[ingredient] = ingredientCount.GetValueOrDefault(ingredient) + 1;
ingredientSet.Add(ingredient);
totalIngredients++;
}
reader.SkipLength("(contains ".Length);
foreach (ReadOnlySpan <byte> allergen in reader.ReadUntil(')').Split(new[] { (byte)',', (byte)' ' }))
{
string allergenStr = Encoding.ASCII.GetString(allergen);
if (allgerenCandidates.TryGetValue(allergenStr, out HashSet <string>?curSet))
{
curSet.IntersectWith(ingredientSet);
}
else
{
allgerenCandidates[allergenStr] = new HashSet <string>(ingredientSet);
}
}
reader.SkipLength(1);
ingredientSet.Clear();
}
int allergenIndex = 0;
string[] allergens = new string[allgerenCandidates.Count];
foreach (string allergen in allgerenCandidates.Keys)
{
allergens[allergenIndex++] = allergen;
}
Array.Sort(allergens);
string?[] ingredients = new string?[allergens.Length];
int part1 = totalIngredients;
for (int allergensLeft = 0; allergensLeft < allergens.Length; allergensLeft++)
{
string foundIngredient = string.Empty;
for (int i = 0; i < allergens.Length; i++)
{
if (ingredients[i] != null)
{
continue;
}
string allergen = allergens[i];
HashSet <string> candidates = allgerenCandidates[allergen];
if (candidates.Count == 1)
{
foundIngredient = candidates.Single();
ingredients[i] = foundIngredient;
part1 -= ingredientCount[foundIngredient];
break;
}
}
foreach (HashSet <string> candidates in allgerenCandidates.Values)
{
candidates.Remove(foundIngredient);
}
}
string part2 = string.Join(',', ingredients);
solution.SubmitPart1(part1);
solution.SubmitPart2(part2);
}
public void Solve(ReadOnlySpan <byte> input, Solution solution)
{
// negative means output, positive means bot
var botOutputs = new Dictionary <int, (bool IsLowBot, int Low, bool IsHighBot, int High)>();
var valueQueue = new Queue <(bool IsBot, int Destination, int Value)>();
int maxBotId = 0;
int maxOutputId = 0;
// first pass we just keep track of where the bot sends its chips
var parser = new SpanReader(input);
while (!parser.Done)
{
if (parser.Peek() == 'b')
{
ParseBotInstruction(ref parser, out int bot, out bool isLowBot, out int low, out bool isHighBot, out int high);
botOutputs[bot] = (isLowBot, low, isHighBot, high);
maxBotId = Math.Max(bot, maxBotId);
if (!isLowBot)
{
maxOutputId = Math.Max(maxOutputId, low);
}
if (!isHighBot)
{
maxOutputId = Math.Max(maxOutputId, high);
}
}
else
{
ParseBotStartingValue(ref parser, out int bot, out int value);
valueQueue.Enqueue((true, bot, value));
}
}
int[]? botValues = new int[maxBotId + 1];
int[]? outputValues = new int[maxOutputId + 1];
int part1 = 0;
while (valueQueue.TryDequeue(out (bool IsBot, int Destination, int Value)x))
{
(bool isBot, int destination, int value) = x;
if (!isBot)
{
outputValues[destination] = value;
continue;
}
int curValue = botValues[destination];
if (curValue == 0)
{
botValues[destination] = value;
}
else
{
(bool IsLowBot, int Low, bool IsHighBot, int High) = botOutputs[destination];
int low = Math.Min(curValue, value);
int high = Math.Max(curValue, value);
if (low == 17 && high == 61)
{
part1 = destination;
}
valueQueue.Enqueue((IsLowBot, Low, low));
valueQueue.Enqueue((IsHighBot, High, high));
}
}
int part2 = outputValues[0] * outputValues[1] * outputValues[2];
solution.SubmitPart1(part1);
solution.SubmitPart2(part2);
}