Building Teams

line = input()

parts = line.split(" ")
pupils, friendships = int(parts[0]), int(parts[1])

adj: dict[int, list[int]] = {}
for i in range(1, pupils + 1):
    adj[i] = []

for _ in range(friendships):
    parts = input().split(" ")
    a, b = int(parts[0]), int(parts[1])

    adj[a].append(b)
    adj[b].append(a)


res: list[str] = []
for i in range(pupils+1):
    res.append("0")

#team = 2, !team = 1
def rec(p: int, team: str):
    
    if res[p] == "1" and team == "2":
        print("IMPOSSIBLE")
        exit(0)

    if res[p] == "2" and team == "1":
        print("IMPOSSIBLE")
        exit(0)

    if res[p] != "0":
        return
    
    res[p] = team
    
    for friend in adj[p]:
        rec(friend, "1" if team == "2" else "2")

for p in range(1, pupils + 1):
    if res[p] == "0":
        rec(p, "1")

print(" ".join(res[1:]))

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "/box/input/code.py", line 43, in <module>
    r...

Test 7

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "/box/input/code.py", line 43, in <module>
    r...

Test 8

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "/box/input/code.py", line 43, in <module>
    r...

Test 9

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "/box/input/code.py", line 43, in <module>
    r...

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED