Course Schedule

import sys
from collections import deque, defaultdict

def main():
  input = sys.stdin.read
  data = input().split()

  n = int(data[0])
  m = int(data[1])

  adj = defaultdict(list)
  in_deg = [0] * (n + 1)
#pre-req
  idx = 2
  for _ in range(m):
    a = int(data[idx])
    b = int(data[idx + 1])
    adj[a].append(b)
    in_deg[b] += 1
    idx += 2

  queue = deque()
  for i in range(1, n + 1):
    if in_deg[i] == 0:
      queue.append(i)

  order = []
  while queue:
    curr = queue.popleft()
    order.append(curr)

    for adjacent in adj[curr]:
      in_deg[adjacent] -= 1
      if in_deg[adjacent] == 0:
        queue.append(adjacent)

  if len(order) == n:
    print(*(order))
  else:
    print("IMPOSSIBLE") #cycle

main()

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: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED