import sys from collections import defaultdict map = [x.strip() for x in sys.stdin] print(map) Y = len(map) X = len(map[0]) assert all(len(row) == X for row in map) N,E,S,W = 1,2,4,8 unknown = 0b11111 grid = {} start = None for i, row in enumerate(map): for j,c in enumerate(row): d = 0 if c == ".": d = 0 elif c == "7": d = W|S elif c == "J": d = N|W elif c == "L": d = N|E elif c == "F": d = S|E elif c == "|": d = N|S elif c == "-": d = W|E elif c == "S": d = unknown start = (i,j) else: raise Exception("invalid char %s at (%s,%s)" % (c, i, j)) grid[i,j] = d #print(grid) def find_loop(grid, start): front = [(0,start)] dist = {} count = defaultdict(int) count[start] -= 1 def push(i,j,from_): if grid.get((i,j),0)&from_: front.append((cost+1, (i,j))) while front: front.sort() cost, n = front.pop(0) if n not in grid: continue count[n] += 1 if n in dist: continue dist[n] = cost i, j = n d = grid[n] if d&N: push(i-1,j,S) if d&S: push(i+1,j,N) if d&W: push(i,j-1,E) if d&E: push(i,j+1,W) #print(count.values()) if not all(c == 2 for c in count.values()): # not a loop return {} return dist def enclosedby(grid, points): # upsample by 3x3 import numpy fill = numpy.zeros((Y*3,X*3+1), dtype='uint8') #fill = [[0]*(X*3) for _ in range(Y*3)] for i,j in points: d = grid[i,j] if d == N|S: t=[[0,1,0],[0,1,0],[0,1,0]] elif d == N|W: t=[[0,1,0],[1,1,0],[0,0,0]] elif d == N|E: t=[[0,1,0],[0,1,1],[0,0,0]] elif d == S|W: t=[[0,0,0],[1,1,0],[0,1,0]] elif d == S|E: t=[[0,0,0],[0,1,1],[0,1,0]] elif d == E|W: t=[[0,0,0],[1,1,1],[0,0,0]] else: raise Exception("invalid d=%d at (%s,%s)" % (d, i, j)) for k in range(3): for l in range(3): fill[i*3+k, j*3+l] = t[k][l] def draw(fill): for row in fill: print("".join(".+O"[f] for f in row)) draw(fill) # fill edges for i in range(Y*3): if fill[i, 0 ] == 0: fill[i, 0 ] = 2 if fill[i, X*3-1] == 0: fill[i, X*3-1] = 2 for j in range(X*3): if fill[ 0 , j] == 0: fill[ 0 , j] = 2 if fill[Y*3-1, j] == 0: fill[Y*3-1, j] = 2 # flood fill changed = True while changed: #draw(fill) changed = False for i in range(Y*3): f = (fill[i] == 2) f = numpy.roll(f, 1) | numpy.roll(f, -1) if i > 0: f |= (fill[i-1] == 2) if i < Y*3-1: f |= (fill[i+1] == 2) f[-1] = False f &= (fill[i] == 0) if f.any(): fill[i, f] = 2 changed = True draw(fill) # downsample inside = [] for i,j in grid: f = [fill[i*3+k, j*3+l]==0 for k in range(3) for l in range(3)] if all(f): inside.append((i,j)) print("inside =", inside) return len(inside) for D in [W|S, N|W, N|E, S|E, N|S, W|E]: grid[start] = D loop = find_loop(grid, start) if loop: print(D, loop.keys()) print(max(loop.values())) print(enclosedby(grid, loop))