I’m trying to solve the “Roads and Bridges” problem on HackerRank https://www.hackerrank.com/challenges/torque-and-development/problem
I believe the code works, but just needs to be optimized for speed. Any advice as to how to approach this? Is the issue the the list comprehension line? Or perhaps the list(unseen) call?
import sys from collections import defaultdict # return connected component containing x def component(graph, x): visited, stack = set(), [x] while len(stack): x = stack.pop() visited.add(x) stack.extend([u for u in graph[x] if u not in visited]) return visited q = int(raw_input().strip()) for a0 in xrange(q): n, m, x, y = raw_input().strip().split(' ') n, m, x, y = [int(n), int(m), long(x), long(y)] roads =  for a1 in xrange(m): city_1, city_2 = raw_input().strip().split(' ') roads.append((int(city_1), int(city_2))) if x <= y: print n * x continue graph = defaultdict(set) for (u, v) in roads: graph[u].add(v) graph[v].add(u) unseen = set(range(1, n+1)) count = 0 while len(unseen): comp = component(graph, list(unseen)) unseen = unseen - comp count += 1 print count * x + (n - count) * y
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