Course Schedule

def topological_sort_dfs(v):
    global result, G, visited, in_use, cyclic
    visited[v] = True
    in_use[v] = True

    for w in G[v]:
        if not visited[w]:
            topological_sort_dfs(w)
        elif in_use[w]:
            cyclic = True
            return


    result.append(v)
    in_use[v] = False


n, m = map(int, input().split())
result = []
visited = [False] * n
in_use = [False] * n
G = [[] for _ in range(n)]
cyclic = False
for _ in range(m):
    a, b = map(int, input().split())
    G[a - 1].append(b - 1)

for v in range(n):
    if not visited[v]:
        topological_sort_dfs(v)
    if cyclic:
        break

if cyclic:
    print('IMPOSSIBLE')
else:
    result.reverse()
    for i in range(n):
        result[i] = result[i] + 1
    print(*result)

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 30, in <module>
    topolo...

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 30, in <module>
    topolo...

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED