# BOJ - 2252 - 줄 세우기

Updated:

```
import sys
from collections import deque
def solution():
N, M = map(int, sys.stdin.readline().split())
graph = [[] for _ in range(N+1)]
degree = [0] * (N+1)
dq = deque()
for _ in range(M):
A, B = map(int, sys.stdin.readline().split())
graph[A].append(B)
degree[B] += 1
for i in range(1, N + 1):
if degree[i] == 0:
dq.append(i)
while dq:
student = dq.popleft()
for j in graph[student]:
degree[j] -= 1
if degree[j] == 0:
dq.append(j)
print(student, end=' ')
solution()
```

https://www.acmicpc.net/problem/2252

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