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Day 15: Replace sortedListReplacement with PriorityQueue 

Use ImmutableHashSet instead of HashSet so visited points do not have to
 be copied
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Stefan Forstenlechner 2021-12-15 23:16:18 +01:00
parent 3be5aca277
commit ee2d1f4bda
1 changed files with 18 additions and 38 deletions
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40
Day15.cs
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@ -1,8 +1,8 @@
#define Day15 #define Day15
using System.Collections.Generic; #if Day15
using System.Collections.Immutable;
using System.Diagnostics; using System.Diagnostics;
using AoC2021; using AoC2021;
#if Day15
var lines = File.ReadAllLines("day15/input"); var lines = File.ReadAllLines("day15/input");
var cave = new int[lines.Length, lines[0].Length]; var cave = new int[lines.Length, lines[0].Length];
@ -29,50 +29,29 @@ long Check(int[,] caveToCheck) {
var pos = new Point(0, 0); var pos = new Point(0, 0);
var end = new Point(caveToCheck.GetLength(0) - 1, caveToCheck.GetLength(1) - 1); var end = new Point(caveToCheck.GetLength(0) - 1, caveToCheck.GetLength(1) - 1);
var visitedLowest = new Dictionary<Point, long>() { { pos, 0 } }; var visitedLowest = new Dictionary<Point, long>() { { pos, 0 } };
long min = 0; var minPaths = new PriorityQueue<PointWithVisited, long>();
var sortedListReplacement = new Dictionary<long, List<PointWithVisited>>() { { 0, new List<PointWithVisited>() { new PointWithVisited(pos, new HashSet<Point>()) } } }; minPaths.Enqueue(new PointWithVisited(pos, ImmutableHashSet.Create<Point>()), 0);
while (true) { while (true) {
if (!sortedListReplacement.ContainsKey(min)) { minPaths.TryDequeue(out PointWithVisited cur, out long min);
min++;
continue;
}
var minPoints = sortedListReplacement[min];
if (minPoints.Count <= 0) {
min++;
continue;
}
var cur = minPoints.First();
if (cur.point.Equals(end)) { if (cur.point.Equals(end)) {
return min; return min;
} }
minPoints.Remove(cur);
var adjacent = GetAdjacent(cur.point, cur.visited, caveToCheck); var adjacent = GetAdjacent(cur.point, cur.visited, caveToCheck);
var nextVisited = cur.visited.Add(cur.point);
foreach (var a in adjacent) { foreach (var a in adjacent) {
var riskLevel = min + caveToCheck[a.row, a.col]; var riskLevel = min + caveToCheck[a.row, a.col];
if (visitedLowest.ContainsKey(a) && visitedLowest[a] <= riskLevel) { if (visitedLowest.ContainsKey(a) && visitedLowest[a] <= riskLevel) {
continue; continue;
} }
visitedLowest[a] = riskLevel; visitedLowest[a] = riskLevel;
AddToCheck(a, riskLevel, cur, sortedListReplacement); minPaths.Enqueue(new PointWithVisited(a, nextVisited), riskLevel);
} }
} }
} }
void AddToCheck(Point p, long sum, PointWithVisited previous, Dictionary<long, List<PointWithVisited>> sortedListReplacement) { List<Point> GetAdjacent(Point cur, ImmutableHashSet<Point> visited, int[,] caveToCheck) {
var copy = previous.visited.ToHashSet();
copy.Add(previous.point);
if (!sortedListReplacement.ContainsKey(sum)) {
sortedListReplacement.Add(sum, new List<PointWithVisited>() {new PointWithVisited(p, copy)});
return;
}
sortedListReplacement[sum].Add(new PointWithVisited(p, copy));
}
List<Point> GetAdjacent(Point cur, HashSet<Point> visited, int[,] caveToCheck) {
return new List<Point>() { return new List<Point>() {
new Point(cur.row + 1, cur.col), new Point(cur.row + 1, cur.col),
new Point(cur.row - 1, cur.col), new Point(cur.row - 1, cur.col),
@ -83,6 +62,7 @@ List<Point> GetAdjacent(Point cur, HashSet<Point> visited, int[,] caveToCheck) {
.ToList(); .ToList();
} }
record PointWithVisited(Point point, HashSet<Point> visited); record PointWithVisited(Point point, ImmutableHashSet<Point> visited);
record Point(int row, int col); record Point(int row, int col);
#endif #endif