[python]백준 11724번:연결 요소의 개수

https://www.acmicpc.net/problem/1172

BFS

from collections import deque
import sys
N, Mmap(int, sys.stdin.readline().split())

graph= [[] for _in range(N+1)]
for i in range(M):
    a, bmap(int, sys.stdin.readline().split())
    graph[a].append(b)
    graph[b].append(a)
	visited= [False]*(N+1)

def bfs(graph, startn, visited):
    queuedeque([startn])
    visited[startn] = True
    while queue:
        curqueue.popleft()
        for i in graph[cur]:
            if not visited[i]:
                queue.append(i)
                visited[i] = True

a=0
for i in range(1, N+1):
    if visited[i]:
        continue
    bfs(graph, i, visited)
    a+= 1
print(a)

dfs

from collections import deque
import sys
limit_number = 15000
sys.setrecursionlimit(limit_number)

N, M = map(int, sys.stdin.readline().split())

graph = [[] for _ in range(N+1)]


for i in range(M):
    a, b = map(int, sys.stdin.readline().split())
    graph[a].append(b)
    graph[b].append(a)

visited = [False]*(N+1)


def dfs(graph, startn, visited):
    visited[startn] = True
    for i in graph[startn]:
        if not visited[i]:
            dfs(graph, i, visited)


a = 0

for i in range(1, N+1):
    if visited[i]:
        continue
    dfs(graph, i, visited)
    a += 1
print(a)

후기

from collections import deque
import sys
N, Mmap(int, sys.stdin.readline().split())

########################################################
graph= {}
for i in range(N):
    graph[i+1] = []
########################################################

for i in range(M):
    a, bmap(int, sys.stdin.readline().split())
    graph[a].append(b)
    graph[b].append(a)
visited= [False]*(N+1)
a=0

def bfs(graph, startn, visited):
   # global a
    b=0
    queuedeque([startn])
    visited[startn] = True
    while queue:
        curqueue.popleft()
        for i in graph[cur]:
            if not visited[i]:
                queue.append(i)
                visited[i] = True
                b=1
    if b== 1:
        a+= 1

for i in range(1, N+1):
    if visited[i]:
        continue
    bfs(graph, i, visited)
print(a)

내가 처음에 작성한 코드

1) 인접리스트를 오랜만에 풀어보아서 그런지 나는 딕셔너리 형태가 편했다.
리스트를 이용해서 0인덱스를 비워두고 1~N 인덱스도 표현할 수 있었다

graph = [ [] for_in range(N+1) ] 

2) 전역변수 사용은 최소화 해야겠다. 백준에서는 오류가 뜬다.