My Advent of Code solutions in Python.
kevinyap.ca/2019/12/going-fast-in-advent-of-code/
advent-of-code
python
Refactor 2017/21 solution
Use dictionary to track each grid sequence.
+18
-21
+18
-21
2017/day21.py
+18
-21
2017/day21.py
···
36
36
for it in range(18):
37
37
# Build up our list of subgrids
38
38
if it % 3 == 0:
39
-
GRIDS = []
40
-
ORIG_GRIDS = []
41
-
for inp in SUBGRIDS:
42
-
GRIDS.append([list(inp[n:n+3]) for n in range(0, 9, 3)])
43
-
ORIG_GRIDS.append(inp)
39
+
GRIDS = {}
40
+
for key in SUBGRIDS:
41
+
GRIDS[key] = [list(key[n:n+3]) for n in range(0, 9, 3)]
44
42
45
-
NEW_GRIDS = []
46
-
for grid in GRIDS:
43
+
for key, grid in GRIDS.items():
47
44
size = len(grid)
48
45
d = 2 if size % 2 == 0 else 3
49
46
···
53
50
for y in range(size // d):
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for x in range(size // d):
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52
# Build the string representation of each 2x2 or 3x3 subgrid
56
-
subgrid = ''
53
+
subgrid = ''.join(
54
+
''.join(grid[y*d + k][x*d:(x+1)*d])
55
+
for k in range(d)
56
+
)
57
57
58
-
for k in range(d):
59
-
subgrid += ''.join(grid[y*d + k][x*d:(x+1)*d])
58
+
# Lookup the corresponding rule and populate the new grid
59
+
rule = RULES[subgrid]
60
60
61
-
# Lookup the corresponding rule and populate the new grid
62
-
out = RULES[subgrid]
63
61
for ny in range(d+1):
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62
for nx in range(d+1):
65
-
new_grid[y*(d+1) + ny][x*(d+1) + nx] = out[ny*(d+1) + nx]
66
-
67
-
NEW_GRIDS.append(new_grid)
63
+
new_grid[y*(d+1) + ny][x*(d+1) + nx] = rule[ny*(d+1) + nx]
68
64
69
-
GRIDS = NEW_GRIDS
65
+
GRIDS[key] = new_grid
70
66
67
+
# Print puzzle output before updating subgrid count
71
68
if it in (4, 17):
72
-
num_pixels = sum(lit_pixels(g) * SUBGRIDS[ORIG_GRIDS[i]] for i, g in enumerate(GRIDS))
73
-
print "Lit pixels after {} iterations:".format(it + 1), num_pixels
69
+
num_pixels = sum(lit_pixels(grid) * SUBGRIDS[key] for key, grid in GRIDS.items())
70
+
print "Lit pixels after {} iterations: {}".format(it + 1, num_pixels)
74
71
75
72
# Update the count of independent 3x3 subgrids
76
73
if it % 3 == 2:
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74
next_subgrids = Counter()
78
-
for i, grid in enumerate(GRIDS):
79
-
mult = SUBGRIDS[ORIG_GRIDS[i]]
75
+
for grid_key, grid in GRIDS.items():
76
+
subgrid_count = SUBGRIDS[grid_key]
80
77
for y in range(0, 9, 3):
81
78
for x in range(0, 9, 3):
82
79
key = ''.join(
83
80
''.join(grid[y+n][x:x+3])
84
81
for n in range(3)
85
82
)
86
-
next_subgrids[key] += mult
83
+
next_subgrids[key] += subgrid_count
87
84
88
85
SUBGRIDS = next_subgrids