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advent-of-code-2021/day-15/day-15.py
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Add day 15 solution
2021-12-15 18:12:05 +01:00

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Python

#!/usr/bin/env python3
from pathlib import Path
def part_1(input):
result = 0
x_size = len(input[0].strip())
y_size = len(input)
nodes = {(x, y): int(v) for y, line in enumerate(input)
for x, v in enumerate(line.strip())}
start = (0, 0)
end = (x_size - 1, y_size - 1)
cost = {start: 0}
prev = {start: None}
queue = set([start])
done = set()
neighbors = set([(-1, 0), (0, -1), (0, 1), (1, 0)])
while len(queue):
cur_cost = None
for n in queue:
if cur_cost == None or cost[n] < cur_cost:
cur_cost = cost[n]
current = n
queue.remove(current)
(xc, yc) = current
next = set()
for (xn, yn) in neighbors:
nbr = (xc + xn, yc + yn)
if nbr in nodes and not nbr in done:
next.add(nbr)
for n in next:
next_cost = cur_cost + nodes[n]
if not n in cost or next_cost < cost[n]:
cost[n] = next_cost
prev[n] = current
queue.add(n)
done.add(current)
result = cost[end]
print("Part 1 result:", result)
def part_2(input):
result = 0
x_size = len(input[0].strip())
y_size = len(input)
repeat = 5
nodes = {}
for y, line in enumerate(input):
for x, v in enumerate(line.strip()):
for i in range(repeat):
for j in range(repeat):
xi = x + (x_size * i)
yj = y + (y_size * j)
vi = (int(v) + i + j)
if 10 <= vi:
vi -= 9
nodes[(xi, yj)] = vi
start = (0, 0)
end = ((x_size * repeat) - 1, (y_size * repeat) - 1)
cost = {start: 0}
prev = {start: None}
queue = set([start])
done = set()
neighbors = set([(-1, 0), (0, -1), (0, 1), (1, 0)])
while len(queue):
cur_cost = None
for n in queue:
if cur_cost == None or cost[n] < cur_cost:
cur_cost = cost[n]
current = n
queue.remove(current)
(xc, yc) = current
next = set()
for (xn, yn) in neighbors:
x = xc + xn
y = yc + yn
if 0 <= x < (x_size * repeat) and 0 <= y < (y_size * repeat):
if not (x, y) in done:
next.add((x, y))
for n in next:
next_cost = cur_cost + nodes[n]
if not n in cost or next_cost < cost[n]:
cost[n] = next_cost
prev[n] = current
queue.add(n)
done.add(current)
result = cost[end]
print("Part 2 result:", result)
input = list()
p = Path(__file__).with_name('input.txt')
with open(p) as f:
input = f.readlines()
part_1(input)
part_2(input)