advent-of-code/2020
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Optimize day 23

Browse Source 
After @tocchan told me how he solved this, I rewrote my solution with
his algorithm in mind and got the runtime down from ~1.3hrs to <250ms
on my desktop PC.
This commit is contained in:
Chris Pickett
2020-12-23 21:28:23 -06:00
parent 29ee7eee26
commit 633beedcc8
1 changed files with 68 additions and 87 deletions
Download Patch File Download Diff File Expand all files Collapse all files

155
Q23.cs
View File

@ -13,15 +13,15 @@ namespace _2020
{
var start = DateTime.Now;
MakeList();
Util.Log($"Q23 MakeList took {(DateTime.Now - start).TotalMilliseconds}ms");
Util.Log($"Q23 MakeList took {(DateTime.Now - start).TotalMilliseconds:N0}ms");
var p1start = DateTime.Now;
Part1();
Util.Log($"Q23 part1 took {(DateTime.Now - p1start).TotalMilliseconds}ms");
Util.Log($"Q23 part1 took {(DateTime.Now - p1start).TotalMilliseconds:N0}ms");
var p2start = DateTime.Now;
Part2();
Util.Log($"Q23 part2 took {(DateTime.Now - p2start).TotalMilliseconds}ms");
Util.Log($"Q23 part2 took {(DateTime.Now - p2start).TotalMilliseconds:N0}ms");
Util.Log($"Q23 took {(DateTime.Now - start).TotalMilliseconds}ms");
Util.Log($"Q23 took {(DateTime.Now - start).TotalMilliseconds:N0}ms");
}
static void MakeList()
@ -33,53 +33,67 @@ namespace _2020
}
}
static int mod(int x, int m)
static int GetNextCup(int[] cupList, int currCup)
{
int r = x;
if (r >= x)
var next = cupList[currCup];
if (next == 0)
{
r = x % m;
return GetNextCup(cupList, next);
}
return next;
}
static void Solve(int[] cupList, int iterations)
{
var currentCup = cupList[0];
var pickedUpCups = new int[3];
for (int move = 0; move < iterations; move++)
{
var pickedUp = GetNextCup(cupList, currentCup);
var nextCup = pickedUp;
for (int i = 0; i < pickedUpCups.Length; i++)
{
pickedUpCups[i] = nextCup;
nextCup = GetNextCup(cupList, nextCup);
}
cupList[currentCup] = nextCup;
var destinationCup = currentCup - 1;
while (pickedUpCups.Contains(destinationCup) || destinationCup == 0)
{
destinationCup--;
if (destinationCup <= 0)
{
destinationCup = cupList.Length - 1;
}
}
var oldDestinationNext = GetNextCup(cupList, destinationCup);
cupList[destinationCup] = pickedUp;
cupList[pickedUpCups[^1]] = oldDestinationNext;
currentCup = GetNextCup(cupList, currentCup);
}
return r < 0 ? r + m : r;
}
static void Part1()
{
var cupList = new List<int>(list);
var currentCupVal = cupList[0];
var currentCupIdx = 0;
var pickedUp = new int[3];
for (int move = 0; move < 100; move++)
var cupList = new int[list.Count + 1];
for (int i = 0, currIdx = 0; i < list.Count; i++)
{
for (int i = currentCupIdx + 1, pickedUpIdx = 0; pickedUpIdx < 3; pickedUpIdx++)
{
if (i >= cupList.Count)
{
i = 0;
}
pickedUp[pickedUpIdx] = cupList[i];
cupList.RemoveAt(i);
}
var destCupVal = currentCupVal - 1;
var destCupIdx = cupList.IndexOf(destCupVal);
while (destCupIdx < 0)
{
destCupVal = mod(destCupVal - 1, cupList.Count + pickedUp.Length + 1);
destCupIdx = cupList.IndexOf(destCupVal);
}
cupList.InsertRange(destCupIdx + 1, pickedUp);
currentCupVal = cupList[mod(cupList.IndexOf(currentCupVal) + 1, cupList.Count)];
currentCupIdx = cupList.IndexOf(currentCupVal);
cupList[currIdx] = list[i];
currIdx = list[i];
}
var startIdx = cupList.IndexOf(1);
Solve(cupList, 100);
var cup = cupList[1];
var scoreStr = "";
for (var idx = startIdx + 1; scoreStr.Length < cupList.Count - 1; idx++)
while (cup != 1)
{
scoreStr += cupList[idx % cupList.Count].ToString();
scoreStr += cup.ToString();
cup = GetNextCup(cupList, cup);
}
Util.Log($"Q23Part1: labels={scoreStr}");
@ -87,58 +101,25 @@ namespace _2020
static void Part2()
{
var cupList = new List<int>(list);
var highestVal = cupList.Aggregate(0, (result, curr) => curr > result ? curr : result);
for (int i = cupList.Count, next = highestVal + 1; i < 1000000; i++, next++)
var cupList = new int[1_000_001];
var currIdx = 0;
foreach (var cup in list)
{
cupList.Add(next);
cupList[currIdx] = cup;
currIdx = cup;
}
var highest = cupList.First(x => cupList[x] == 0);
cupList[highest] = list.Count + 1;
for (int i = cupList[highest]; i < cupList.Length; i++)
{
cupList[i] = i == cupList.Length - 1 ? 0 : i + 1;
}
var currentCupVal = cupList[0];
var currentCupIdx = 0;
var pickedUp = new int[3];
var start = DateTime.Now;
var lastMove = 0;
for (int move = 0; move < 10000000; move++)
{
for (int i = currentCupIdx + 1, pickedUpIdx = 0; pickedUpIdx < 3; pickedUpIdx++)
{
if (i >= cupList.Count)
{
i = 0;
}
Solve(cupList, 10_000_000);
pickedUp[pickedUpIdx] = cupList[i];
cupList.RemoveAt(i);
}
var destCupVal = currentCupVal - 1;
var destCupIdx = cupList.IndexOf(destCupVal);
while (destCupIdx < 0)
{
destCupVal = mod(destCupVal - 1, cupList.Count + pickedUp.Length + 1);
destCupIdx = cupList.IndexOf(destCupVal);
}
cupList.InsertRange(destCupIdx + 1, pickedUp);
currentCupVal = cupList[mod(cupList.IndexOf(currentCupVal) + 1, cupList.Count)];
currentCupIdx = cupList.IndexOf(currentCupVal);
var dt = DateTime.Now - start;
var dtSeconds = dt.TotalSeconds;
if (dtSeconds >= 1.0)
{
start = DateTime.Now;
var rate = (move - lastMove) / dtSeconds;
lastMove = move;
var remainingMoves = 10000000 - move;
var endTime = DateTime.Now + TimeSpan.FromSeconds(remainingMoves / rate);
Util.Log($"Current rate: {rate:N1} mps, {remainingMoves:N} moves remaining. Should be done by {endTime}");
}
}
var oneIdx = cupList.IndexOf(1);
Util.Log($"Q23Part2: next two={cupList[(oneIdx + 1) % cupList.Count]}, {cupList[(oneIdx + 2) % cupList.Count]}, multiplied={1L * cupList[(oneIdx + 1) % cupList.Count] * cupList[(oneIdx + 2) % cupList.Count]}");
var first = cupList[1];
var second = cupList[first];
Util.Log($"Q23Part2: first={first}, second={second}, mult={1L * first * second}");
}
}
}