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Day 17 solution

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This is very slow. There are lots of ways to optimize it, but I hate this problem so I probably won't come back to it. But maybe.
This commit is contained in:
Chris Pickett
2022-12-17 01:55:17 -06:00
parent fcfdb7146b
commit 09f866c9a3
5 changed files with 241 additions and 3 deletions
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1
advent-of-code-2022.csproj
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@ -71,6 +71,7 @@
<None Remove="inputs\17.txt" />
<EmbeddedResource Include="inputs\17.txt" />
<None Remove="inputs\18.txt" />
<EmbeddedResource Include="inputs\17a.txt" />
<EmbeddedResource Include="inputs\18.txt" />
<None Remove="inputs\19.txt" />
<EmbeddedResource Include="inputs\19.txt" />

2
inputs/17.txt
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File diff suppressed because one or more lines are too long

1
inputs/17a.txt Normal file
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@ -0,0 +1 @@
>>><<><>><<<>><>>><<<>>><<<><<<>><>><<>>

236
src/17.cs Normal file
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@ -0,0 +1,236 @@
using aoc2022.Util;
namespace aoc2022;
internal class Day17 : Day
{
private List<bool> jetPatterns = new();
private ivec2[][] rocks =
{
new[]{
new ivec2(0, 0),
new ivec2(1, 0),
new ivec2(2, 0),
new ivec2(3, 0),
},
new[]{
new ivec2(0, 1),
new ivec2(1, 0),
new ivec2(1, 1),
new ivec2(1, 2),
new ivec2(2, 1),
},
new[]{
new ivec2(0, 2),
new ivec2(1, 2),
new ivec2(2, 0),
new ivec2(2, 1),
new ivec2(2, 2),
},
new[]{
new ivec2(0, 0),
new ivec2(0, 1),
new ivec2(0, 2),
new ivec2(0, 3),
},
new[]{
new ivec2(0, 0),
new ivec2(0, 1),
new ivec2(1, 0),
new ivec2(1, 1),
},
};
internal override void Parse()
{
var content = Parsing.ReadAllText("17");
foreach (var ch in content)
{
jetPatterns.Add(ch == '>');
}
}
private const int maxWidth = 7;
private bool canMove(int rockIdx, ivec2 rockPos, ICollection<ivec2> grid, ivec2 direction)
{
var rock = rocks[rockIdx];
var rockWidth = rock.MaxBy(v => v.x).x + 1;
var rockHeight = rock.MaxBy(v => v.y).y;
var result = rockPos + direction;
if (result.x < 0)
{
return false;
}
if (result.x + rockWidth > maxWidth)
{
return false;
}
if (result.y - rockHeight == -1)
{
return false;
}
foreach (var pt in rock)
{
if (grid.Contains(result + new ivec2(pt.x, -pt.y)))
{
return false;
}
}
return true;
}
internal override string Part1()
{
int settledRocks = 0;
HashSet<ivec2> grid = new();
int jetSteps = 0;
for (int idx = 0; settledRocks < 2022; idx++)
{
var rockIdx = idx % rocks.Length;
var maxHeight = grid.Count > 0 ? grid.MaxBy(v => v.y).y + 1 : 0;
var rockHeight = rocks[rockIdx].MaxBy(v => v.y).y;
var rockPos = new ivec2(2, maxHeight + rockHeight + 3);
bool settled = false;
while (!settled)
{
var jetIdx = jetSteps % jetPatterns.Count;
jetSteps++;
if (jetPatterns[jetIdx])
{
if (canMove(rockIdx, rockPos, grid, ivec2.RIGHT))
{
rockPos.x++;
}
}
else
{
if (canMove(rockIdx, rockPos, grid, ivec2.LEFT))
{
rockPos.x--;
}
}
// inverted up/down for this...
if (canMove(rockIdx, rockPos, grid, ivec2.UP))
{
rockPos.y--;
}
else
{
settled = true;
}
if (settled)
{
foreach (var pt in rocks[rockIdx])
{
grid.Add(rockPos + new ivec2(pt.x, -pt.y));
}
settledRocks++;
}
}
}
var finalMaxHeight = grid.MaxBy(v => v.y).y + 1;
return $"After <green>2022<+black> rocks, tower height is: <+white>{finalMaxHeight}";
}
internal override string Part2()
{
long settledRocks = 0;
HashSet<ivec2> grid = new();
List<long> heightDeltasPerStep = new();
long jetSteps = 0;
for (long idx = 0; settledRocks < 10000; idx++)
{
var rockIdx = (int)(idx % rocks.Length);
var maxHeight = grid.Count > 0 ? grid.MaxBy(v => v.y).y + 1 : 0;
var rockHeight = rocks[rockIdx].MaxBy(v => v.y).y;
var rockPos = new ivec2(2, maxHeight + rockHeight + 3);
bool settled = false;
while (!settled)
{
var jetIdx = (int)(jetSteps % jetPatterns.Count);
jetSteps++;
if (jetPatterns[jetIdx])
{
if (canMove(rockIdx, rockPos, grid, ivec2.RIGHT))
{
rockPos.x++;
}
}
else
{
if (canMove(rockIdx, rockPos, grid, ivec2.LEFT))
{
rockPos.x--;
}
}
// inverted up/down for this...
if (canMove(rockIdx, rockPos, grid, ivec2.UP))
{
rockPos.y--;
}
else
{
settled = true;
}
if (settled)
{
foreach (var pt in rocks[rockIdx])
{
grid.Add(rockPos + new ivec2(pt.x, -pt.y));
}
settledRocks++;
var newMaxHeight = grid.MaxBy(v => v.y).y + 1;
heightDeltasPerStep.Add(newMaxHeight - maxHeight);
}
}
}
int cycleSize = 0;
int skip = 0;
for (int jumpAhead = 250; jumpAhead < 500 && skip == 0; jumpAhead++)
{
var skipped = heightDeltasPerStep.Skip(jumpAhead);
for (int cycleLen = 100; cycleLen < heightDeltasPerStep.Count / 4; cycleLen++)
{
var chunked = skipped.Chunk(cycleLen);
if (chunked.All(c => c.Length < cycleLen || c.SequenceEqual(chunked.First())))
{
skip = jumpAhead;
cycleSize = cycleLen;
break;
}
}
}
if (skip == 0)
{
throw new Exception("cycle not found");
}
var baseHeight = heightDeltasPerStep.Take(skip).Sum();
var chunkHeight = heightDeltasPerStep.Skip(skip).Take(cycleSize).Sum();
var cumulativeHeight = baseHeight;
long simmed;
for (simmed = skip; simmed + cycleSize < 1000000000000; simmed += cycleSize)
{
cumulativeHeight += chunkHeight;
}
var finalChunkHeight = heightDeltasPerStep.Skip(skip).Take((int)(1000000000000 - simmed)).Sum();
cumulativeHeight += finalChunkHeight;
return $"After skipping <green>{skip}<+black> initial drops, a cycle of size <green>{cycleSize}<+black> produced a final height of <+white>{cumulativeHeight}";
}
}

4
src/Util/Vec2.cs
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@ -2,8 +2,8 @@
public struct ivec2 : IEquatable<ivec2>, IComparable<ivec2>, IComparable
{
public readonly long x = 0;
public readonly long y = 0;
public long x = 0;
public long y = 0;
public static readonly ivec2 ZERO = new ivec2(0, 0);
public static readonly ivec2 ONE = new ivec2(1, 1);