Created
February 10, 2015 16:00
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import string | |
from collections import defaultdict | |
from heapq import heappop, heappush | |
class UnionFind(object): | |
def __init__(self, size): | |
# not enough | |
self.size = defaultdict(int) | |
self.weights = range(size) | |
def union(self, a, b): | |
# Get index roots | |
root_a = self._root(a) | |
root_b = self._root(b) | |
# Added some balancing | |
if self.size[root_a] > self.size[root_b]: | |
self.weights[root_b] = self.weights[root_a] | |
self.size[root_a] += self.size[root_b] | |
else: | |
self.weights[root_a] = self.weights[root_b] | |
self.size[root_b] += self.size[root_a] | |
def iter_weights(self): | |
for idx in xrange(len(self.weights)): | |
yield self._root(idx) | |
def _root(self, idx): | |
last = idx | |
while self.weights[last] != last: | |
last = self.weights[last] | |
return last | |
def get_neighbours(matrix, idx, width, height): | |
y = idx / width | |
x = idx % width | |
res = [] | |
order_of_importance = iter(xrange(0, 4)) | |
if y - 1 >= 0: | |
key = (y-1) * width + x | |
heappush(res, (matrix[key], next(order_of_importance), key)) | |
if x - 1 >= 0: | |
key = y * width + (x - 1) | |
heappush(res, (matrix[key], next(order_of_importance), key)) | |
if x + 1 < width: | |
key = y * width + (x + 1) | |
heappush(res, (matrix[key], next(order_of_importance), key)) | |
if y + 1 < height: | |
key = (y+1) * width + x | |
heappush(res, (matrix[key], next(order_of_importance), key)) | |
# Better use a heap | |
return heappop(res) | |
def main(): | |
with open('B-large-practice.in') as f: | |
n_cases = int(f.readline()) | |
for n in xrange(n_cases): | |
# Pluck width and height | |
height, width = map(int, f.readline().split(' ')) | |
# Create union find datastructure | |
uf = UnionFind(width * height) | |
matrix = [] | |
for _ in xrange(height): | |
matrix.extend(map(int, f.readline().split(' '))) | |
for idx, el in enumerate(matrix): | |
try: | |
cost, _, neighbour_id = get_neighbours(matrix, idx, width, height) | |
except IndexError: | |
continue | |
if cost < el: | |
uf.union(idx, neighbour_id) | |
print "Case #%s:" % (n + 1) | |
letters = iter(string.ascii_lowercase) | |
d = {} | |
iter_weights = uf.iter_weights() | |
for _ in xrange(height): | |
cs = [] | |
for _ in xrange(width): | |
num = next(iter_weights) | |
try: | |
cs.append(d[num]) | |
except KeyError: | |
char = d[num] = next(letters) | |
cs.append(char) | |
print ' '.join(cs) | |
if __name__ == '__main__': | |
main() |
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