Building Teams

import sys
from collections import deque

#build adjacecny and get input
input_data = sys.stdin.read().split()#get whole input data at once
n_pupils = int(input_data[0])
n_friendships = int(input_data[1])

adj = [[] for _ in range(n_pupils+1)]

k = 2



for _ in range(n_friendships):
    a = int(input_data[k])
    b = int(input_data[k+1])
    adj[a].append(b)
    adj[b].append(a)
    k+=2


def run_bfs(adj):
    #gonna run bfs for every component

    visited = [False] * (n_pupils+1)
    teams = [0]*(n_pupils+1)

    for i in range(1,n_pupils+1):
        if not visited[i]:
            bfs(adj, i, visited, teams)
    print(*list(map(str,teams[1:])))

def bfs(adj,src,visited,teams):
    #for each component gontta start from a specifc person, attribute a role to him  arbitraly then spread to neighbors
    q = deque()
    q.append(src)
    visited[src]=True
    teams[src]=1

    while(q):
        current = q.popleft()

        for n in adj[current]:
            if not visited[n]:
                visited[n] = True
                teams[n] = 1 if teams[current] == 2 else 2
                q.append(n)
            elif teams[current] == teams[n]:
                print("IMPOSSIBLE")
                exit()

run_bfs(adj)

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