# BOJ - 5567 - 1학년

Updated:

```
import sys
from collections import deque
def BFS(graph, N):
visit = [False] * (N + 1)
dq = deque()
dq.append((1, 1))
visit[1] = 1
while dq:
vertex, weight = dq.popleft()
for v in graph[vertex]:
if visit[v] is False:
visit[v] = weight + 1
dq.append((v, weight + 1))
return visit
def solution():
N = int(input())
M = int(input())
graph = [[] for _ in range(N+1)]
for _ in range(M):
a, b = map(int, sys.stdin.readline().split())
graph[a].append(b)
graph[b].append(a)
visit = BFS(graph, N)
ret = 0
for v in visit:
if 2 <= v < 4:
ret += 1
print(ret)
solution()
```

https://www.acmicpc.net/problem/5567

## Leave a comment