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day 23
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‎2021/Day23/Solution.cs

Lines changed: 97 additions & 88 deletions
Original file line numberDiff line numberDiff line change
@@ -27,32 +27,16 @@ int Solve(string input) {
2727
q.Enqueue(maze, 0);
2828
cost.Add(maze, 0);
2929

30-
bool finished(Maze maze) {
31-
bool colMatch(int icol, char c) {
32-
for (var pt = new Point(2, icol); maze.ItemAt(pt) != '#'; pt = pt.Below) {
33-
if (maze.ItemAt(pt) != c) {
34-
return false;
35-
}
36-
}
37-
return true;
38-
}
39-
return colMatch(3, 'A') && colMatch(5, 'B') && colMatch(7, 'C') && colMatch(9, 'D');
40-
}
41-
4230
while (q.Count > 0) {
43-
while (cost[q.UnorderedItems.First().Element] != q.UnorderedItems.First().Priority) {
44-
q.Dequeue();
45-
}
46-
47-
maze = q.Dequeue();;
31+
maze = q.Dequeue();
4832

49-
if (finished(maze)) {
33+
if (maze.Finished()) {
5034
return cost[maze];
5135
}
5236

5337
foreach (var n in Neighbours(maze)) {
54-
if (n.cost + cost[maze] < cost.GetValueOrDefault(n.maze, int.MaxValue)) {
55-
cost[n.maze] = n.cost + cost[maze];
38+
if (cost[maze] + n.cost < cost.GetValueOrDefault(n.maze, int.MaxValue)) {
39+
cost[n.maze] = cost[maze] + n.cost;
5640
q.Enqueue(n.maze, cost[n.maze]);
5741
}
5842
}
@@ -63,10 +47,11 @@ bool colMatch(int icol, char c) {
6347

6448
Maze GetMaze(string input) {
6549
var map = input.Split("\n");
66-
var maze = new Maze(0, 0, 0, 0, map.Length > 6);
67-
foreach (var y in Enumerable.Range(0, map.Length)) {
68-
foreach (var x in Enumerable.Range(0, map[0].Length)) {
69-
maze = maze.SetItem(new Point(y, x), y < map.Length && x < map[y].Length ? map[y][x] : '#');
50+
var maze = new Maze(map.Length > 6);
51+
foreach (var irow in Enumerable.Range(0, map.Length)) {
52+
foreach (var icol in Enumerable.Range(0, map[0].Length)) {
53+
maze = maze.SetItem(
54+
new Point(irow, icol), irow < map.Length && icol < map[irow].Length ? map[irow][icol] : '#');
7055
}
7156
}
7257
return maze;
@@ -76,15 +61,6 @@ int stepCost(char actor) {
7661
return actor == 'A' ? 1 : actor == 'B' ? 10 : actor == 'C' ? 100 : 1000;
7762
}
7863

79-
char getChDst(int icol) {
80-
return
81-
icol == 3 ? 'A' :
82-
icol == 5 ? 'B' :
83-
icol == 7 ? 'C' :
84-
icol == 9 ? 'D' :
85-
throw new Exception();
86-
}
87-
8864
int getIcolDst(char ch) {
8965
return
9066
ch == 'A' ? 3 :
@@ -94,19 +70,7 @@ int getIcolDst(char ch) {
9470
throw new Exception();
9571
}
9672

97-
bool finishedColumn(Maze maze, int icol) {
98-
var pt = new Point(2, icol);
99-
var chDst = getChDst(icol);
100-
while (maze.ItemAt(pt) != '#') {
101-
if (maze.ItemAt(pt) != chDst) {
102-
return false;
103-
}
104-
pt = pt.Below;
105-
}
106-
return true;
107-
}
108-
109-
IEnumerable<(Maze maze, int cost)> Neighbours(Maze maze) {
73+
(Maze maze, int cost) HallwayToRoom(Maze maze) {
11074

11175
bool columnIsClean(int icol, char ch) {
11276
var pt = new Point(2, icol);
@@ -133,44 +97,38 @@ Point step(Point pt) {
13397
return true;
13498
}
13599

136-
// le-e lehet menni?
137-
(Maze maze, int cost) Lemegy(Maze maze) {
138-
for (var icol = 1; icol < 12; icol++) {
139-
var ch = maze.ItemAt(new Point(1, icol));
140-
141-
if (ch == '.') {
142-
continue;
143-
}
100+
for (var icol = 1; icol < 12; icol++) {
101+
var ch = maze.ItemAt(new Point(1, icol));
144102

145-
var icolDst = getIcolDst(ch);
103+
if (ch == '.') {
104+
continue;
105+
}
146106

147-
if (rowIsClean(icol, icolDst) && columnIsClean(icolDst, ch)) {
148-
var steps = Math.Abs(icolDst - icol);
149-
var pt = new Point(1, icolDst);
107+
var icolDst = getIcolDst(ch);
150108

151-
while (maze.ItemAt(pt.Below) == '.') {
152-
pt = pt.Below;
153-
steps++;
154-
}
109+
if (rowIsClean(icol, icolDst) && columnIsClean(icolDst, ch)) {
110+
var steps = Math.Abs(icolDst - icol);
111+
var pt = new Point(1, icolDst);
155112

156-
var l = Lemegy(maze.SetItem(new Point(1, icol), '.').SetItem(pt, ch));
157-
return (l.maze, l.cost + steps * stepCost(ch));
113+
while (maze.ItemAt(pt.Below) == '.') {
114+
pt = pt.Below;
115+
steps++;
158116
}
117+
118+
var l = HallwayToRoom(maze.SetItem(new Point(1, icol), '.').SetItem(pt, ch));
119+
return (l.maze, l.cost + steps * stepCost(ch));
159120
}
160-
return (maze, 0);
161121
}
122+
return (maze, 0);
123+
}
162124

163-
var lemegy = Lemegy(maze);
164-
if (lemegy.cost != 0) {
165-
yield return lemegy;
166-
yield break;
167-
}
125+
IEnumerable<(Maze maze, int cost)> RoomToHallway(Maze maze) {
168126
var allowedHColumns = new int[] { 1, 2, 4, 6, 8, 10, 11 };
169127

170128
// fel lehet-e menni
171129
foreach (var icol in new[] { 3, 5, 7, 9 }) {
172130

173-
if (finishedColumn(maze, icol)) {
131+
if (maze.FinishedColumn(icol)) {
174132
continue;
175133
}
176134

@@ -192,10 +150,11 @@ Point step(Point pt) {
192150
while (maze.ItemAt(ptDst) == '.') {
193151

194152
if (allowedHColumns.Contains(ptDst.icol)) {
195-
yield return (
196-
maze.SetItem(ptSrc, '.').SetItem(ptDst, ch),
197-
(stepsV + stepsH) * stepCost(ch)
198-
);
153+
var mazeT = maze.SetItem(ptSrc, '.').SetItem(ptDst, ch);
154+
var c = (stepsV + stepsH) * stepCost(ch);
155+
// (mazeT, c) = (Lemegy(mazeT).maze, c + Lemegy(mazeT).cost);
156+
157+
yield return (mazeT, c);
199158
}
200159

201160
if (dj == -1) {
@@ -209,6 +168,11 @@ Point step(Point pt) {
209168
}
210169
}
211170

171+
IEnumerable<(Maze maze, int cost)> Neighbours(Maze maze) {
172+
var hallwayToRoom = HallwayToRoom(maze);
173+
return hallwayToRoom.cost != 0 ? new[] { hallwayToRoom } : RoomToHallway(maze);
174+
}
175+
212176
}
213177

214178
record Point(int irow, int icol) {
@@ -217,7 +181,22 @@ record Point(int irow, int icol) {
217181
public Point Left => new Point(irow, icol - 1);
218182
public Point Right => new Point(irow, icol + 1);
219183
}
220-
record Maze(int a, int b, int c, int d, bool big) {
184+
185+
record Maze {
186+
187+
bool big;
188+
int a, b, c, d;
189+
190+
public Maze(bool big) : this(0, 0, 0, 0, big) {
191+
}
192+
193+
private Maze(int a, int b, int c, int d, bool big) {
194+
this.a = a;
195+
this.b = b;
196+
this.c = c;
197+
this.d = d;
198+
this.big = big;
199+
}
221200

222201
int BitFromPoint(Point pt) =>
223202
(big, pt.irow, pt.icol) switch {
@@ -256,6 +235,37 @@ int BitFromPoint(Point pt) =>
256235
_ => 1 << 31,
257236
};
258237

238+
private int ColumnMask(char ch) {
239+
if (big) {
240+
switch (ch) {
241+
case 'A': return (1 << 11) | (1 << 15) | (1 << 19) | (1 << 23);
242+
case 'B': return (1 << 12) | (1 << 16) | (1 << 20) | (1 << 24);
243+
case 'C': return (1 << 13) | (1 << 17) | (1 << 21) | (1 << 25);
244+
case 'D': return (1 << 14) | (1 << 18) | (1 << 22) | (1 << 26);
245+
}
246+
} else {
247+
switch (ch) {
248+
case 'A': return (1 << 11) | (1 << 15);
249+
case 'B': return (1 << 12) | (1 << 16);
250+
case 'C': return (1 << 13) | (1 << 17);
251+
case 'D': return (1 << 14) | (1 << 18);
252+
}
253+
}
254+
throw new Exception();
255+
}
256+
257+
public bool FinishedColumn(int icol) =>
258+
icol switch {
259+
3 => (a & ColumnMask('A')) == ColumnMask('A'),
260+
5 => (b & ColumnMask('B')) == ColumnMask('B'),
261+
7 => (c & ColumnMask('C')) == ColumnMask('C'),
262+
9 => (d & ColumnMask('D')) == ColumnMask('D'),
263+
_ => throw new Exception()
264+
};
265+
266+
public bool Finished() =>
267+
FinishedColumn(3) && FinishedColumn(5) && FinishedColumn(7) && FinishedColumn(9);
268+
259269
public char ItemAt(Point pt) {
260270
var bit = BitFromPoint(pt);
261271
return
@@ -264,7 +274,6 @@ public char ItemAt(Point pt) {
264274
(b & bit) != 0 ? 'B' :
265275
(c & bit) != 0 ? 'C' :
266276
(d & bit) != 0 ? 'D' :
267-
(d & bit) != 0 ? 'D' :
268277
'.';
269278
}
270279

@@ -277,17 +286,17 @@ public Maze SetItem(Point pt, char ch) {
277286
}
278287

279288
return ch switch {
280-
'.' =>
281-
this with {
282-
a = a & ~bit,
283-
b = b & ~bit,
284-
c = c & ~bit,
285-
d = d & ~bit
286-
},
287-
'A' => this with { a = a | bit },
288-
'B' => this with { b = b | bit },
289-
'C' => this with { c = c | bit },
290-
'D' => this with { d = d | bit },
289+
'.' => new Maze(
290+
a & ~bit,
291+
b & ~bit,
292+
c & ~bit,
293+
d & ~bit,
294+
big
295+
),
296+
'A' => new Maze(a | bit, b, c, d, big),
297+
'B' => new Maze(a, b | bit, c, d, big),
298+
'C' => new Maze(a, b, c | bit, d, big),
299+
'D' => new Maze(a, b, c, d | bit, big),
291300
_ => throw new Exception()
292301
};
293302
}

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