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>2x speedup for part 2

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Based on a suggestion from @tocchan I converted the total risk map from a Dictionary to an array and things really took off (125ms to 50ms on my machine in Release). And that's with a sub-optimal fill/memset of the array to int.MaxValue (which I couldn't find a better way to do without diving into `unsafe` territory), though that step only takes about 500us with this method anyway, so it's hardly the worst part.
This commit is contained in:
Chris Pickett
2021-12-15 12:15:31 -06:00
parent eb45460f21
commit 84c7f424ba
1 changed files with 14 additions and 8 deletions
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22
src/15.cs
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@ -42,30 +42,36 @@ internal class Day15 : Day
private static int Solve(byte[,] riskMap)
{
var start = (x: 0, y: 0);
var end = (x: riskMap.GetLength(0) - 1, y: riskMap.GetLength(1) - 1);
var (xDim, yDim) = (riskMap.GetLength(0), riskMap.GetLength(1));
var end = (x: xDim - 1, y: yDim - 1);
var q = new PriorityQueue<(int, int), int>();
q.Enqueue(start, 0);
var totalRiskMap = new Dictionary<(int, int), int>
var totalRiskMap = new int[xDim, yDim];
for (int x = 0; x < xDim; x++)
{
[start] = 0
};
for (int y = 0; y < yDim; y++)
{
totalRiskMap[x, y] = int.MaxValue;
}
}
totalRiskMap[start.x, start.y] = 0;
for (var currPoint = start; currPoint != end; currPoint = q.Dequeue())
{
foreach (var adjacent in Adjacent(riskMap, currPoint.x, currPoint.y))
{
var totalRiskThroughP = totalRiskMap[currPoint] + riskMap[adjacent.x, adjacent.y];
if (totalRiskThroughP < totalRiskMap.GetValueOrDefault(adjacent, int.MaxValue))
var totalRiskThroughP = totalRiskMap[currPoint.x, currPoint.y] + riskMap[adjacent.x, adjacent.y];
if (totalRiskThroughP < totalRiskMap[adjacent.x, adjacent.y])
{
totalRiskMap[adjacent] = totalRiskThroughP;
totalRiskMap[adjacent.x, adjacent.y] = totalRiskThroughP;
q.Enqueue(adjacent, totalRiskThroughP);
}
}
}
return totalRiskMap[end];
return totalRiskMap[end.x, end.y];
}
private static void Part1(byte[,] grid)