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#advent of code 2024
#day 16
#version 1 - not cleaned up
#don't know anymore, can't explain - keeping the unrevised version because it's hilariously dogshit
#part 1: simple shortest path search
#part 2: keep the path searching function running until all paths with distance equal to the shortest path are registered
#keep track of distance for each node, kinda like djikstra, distance to each node is stored in a dictionary
#with only exception that it stores all of the possible
#in short: linked list, in format: node_1:set_of_previous_nodes, previous nodes have shortest possible path to that node
#keep a map of previous steps, that is Position_now:set of positions that could be used to reach
#I also commented out a check to prevent going backwards (take step north, then take step south)
#but I guess that was taken care of during other checks like how big is the distance so it didnt matter
#the entries in queues with distance greater than registered shortest path are discarded
#the check is repeated (probably unnecessarily) before queuepush
#my other issue: there could be more than 1 directions from which I could reach the E
#while I registered all of them, durign testing I used only one of them
#turns out there weren't multiple ends (all valid paths reach E from the same direction)
#sidenote: i think i solved that earlier, because I was getting similar values, but I didn't bother to check
#assumptions:
#only 1 starting position
import heapq
grid = {};
xMin, yMin, xMax, yMax = 0,0,0,0; #just for printout
dirs = [(1,0),(0,1),(-1,0),(0,-1)]; #east, south, west, north
f = open("16.in","r");
for y,l in enumerate(f):
yMax = max(y,yMax);
for x,c in enumerate(l.strip()):
if c == "S":
start = (x,y);
c = "."
grid[(x,y)]=c;
xMax = max(xMax,x);
f.close();
'''
for y in range(yMax+1):
for x in range(xMax+1):
print(grid[(x,y)], end="");
print(); #'''
#print(start);
def getAdjacent(coordinates):
adj = [];
xp, yp, dp = coordinates;
for i,d in enumerate(dirs):
dx,dy = d;
if grid.get((xp+dx,yp+dy),"#") != "#":
adj.append((xp+dx,yp+dy,i));
return adj;
BigNumber = xMax*yMax*100000000000;
def pathfinding(startingpos):
ends = set();
visited = set();
x0,y0 = startingpos;
queue = [];
heapq.heappush(queue,(0,(x0,y0,0)));
ShortestPath = BigNumber;
pathmap = {};
pathdis = {};
pathmap[(x0,y0,0)] = set();
while queue:
distance, coords = heapq.heappop(queue);
#if coords in visited: continue;
if distance > ShortestPath: continue;
visited.add(coords);
px,py,pd = coords;
#pathmap[(coords,prevs)] = min(distance, pathmap.get((coords,prevs),float('inf')));
CurrentTile = grid.get((px,py),"#");
if CurrentTile == "E":
ShortestPath = min(ShortestPath,distance);
if distance == ShortestPath:
ends.add(coords);
#else:
NextValid = getAdjacent((px,py,pd));
for NV in NextValid:
#print("NV", distance+1+1000*(NV[2]!=pd),NV);
next_dist = distance+1+1000*(NV[2]!=pd);
prev_dist = pathdis.get(NV,BigNumber);
if next_dist > prev_dist:
continue;
if next_dist < prev_dist:
pathmap[NV] = set();
pathdis[NV] = next_dist;
pathmap[NV].add(coords);
#if NV[2] == (pd+2)%4: continue;
heapq.heappush(queue,(distance+1+1000*(NV[2]!=pd),NV));
return ShortestPath, pathmap, pathdis, ends;
part1, PathMap,PathDis, PathEnds = pathfinding(start);
part2 = len(PathMap);
newtotal = set();
#for shit in tv:
# shit1,shit2,shit2
print("part 1 =", part1);
#print(PathMap);
for pm in PathMap:
if len(PathMap[pm]) > 1:
print(pm, PathMap[pm]);
#input();
#print(PathDis);
#input();
#print(PathEnds);
def FindSpots(startpos,end,pathmap,pathdis,prevpaths):
#sx,sy,_ =
validpaths = set();
print(end);
#for end in endpos:
#queue = [end];
#scorereversed = 0 + pathdis[end];
CurrentPosition = end;
validpaths.add(CurrentPosition);
#while queue:
# x,y,d = queue.pop();
if end == startpos:
return validpaths;
#x,y,d = end;
NextPositions = pathmap[end];
for np in NextPositions:
validpaths.update(FindSpots(startpos,np,pathmap,pathdis,validpaths.copy()));
return validpaths;
print("FINSPOTS");
FirstEnd = PathEnds.pop();
testing = FindSpots(start,FirstEnd,PathMap,PathDis,set());
print("testing");
print(testing);
print(len(testing));
storeshit = set();
for t in testing:
tx,ty,td = t;
storeshit.add((tx,ty));
for y in range(yMax+1):
for x in range(xMax+1):
c = grid[(x,y)];
#if (x,y) in tv:
# c = "O";
counter = 0;
for ind in range(4):
if (x,y,ind) in testing: counter += 1;
if counter != 0: c = str(counter);
##c = "O";
#break;#'''
print(c, end="");
print();
print("part 1 =", part1);
print("part 2 =", len(storeshit));
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