Problem p02678 (python)

Fixed submission:
import sys
import queue
n,m = map(int, sys.stdin.readline().rstrip("\n").split())
adj = [[]for i in range(n+1)]
parent = [-1] * (n+1)
for line in sys.stdin:
    a,b = map(int, line.rstrip("\n").split())
    adj[a].append(b)
    adj[b].append(a)
q = queue.Queue()
q.put((1,0))
while(not q.empty()):
    x, p = q.get()
    if parent[x] != -1: # 訪問済み
        continue
    parent[x] = p
    for next in adj[x]:
        if parent[next] == -1: # 未訪問なら
            q.put((next,x))
print ('Yes') # 必ず目標は達成できる
for p in parent[2:]: # 部屋2以降の親（前の部屋）
    print(p)

Buggy submission (verdict: Runtime Error):
import sys
n,m = map(int, sys.stdin.readline().rstrip("\n").split())
adj = [[]for i in range(n+1)]
parent = [-1] * (n+1)
for line in sys.stdin:
    a,b = map(int, line.rstrip("\n").split())
    adj[a].append(b)
    adj[b].append(a)
q = queue.Queue()
q.put((1,0))
while(not q.empty()):
    x, p = q.get()
    if parent[x] != -1: # 訪問済み
        continue
    parent[x] = p
    for next in adj[x]:
        if parent[next] == -1: # 未訪問なら
            q.put((next,x))
print ('Yes') # 必ず目標は達成できる
for p in parent[2:]: # 部屋2以降の親（前の部屋）
    print(p)

Buggy submission (verdict: Runtime Error):
import sys
n,m = map(int, sys.stdin.readline().rstrip("\n").split())
cage = {}
for i in range (2,n+1):
    cage[i] = None
ab = [map(int, line.rstrip("\n").split()) for line in sys.stdin]
a,b = [list(i) for i in zip(*ab)]
room = [1]
nroom = []
while None in cage.values():
    for i in range(len(room)):
        j = 0
        while j < (len(a)):
            if a[j] == room[i]:
                if cage[b[j]] == None:
                    cage[b[j]] = a[j]
                nroom.append(b[j])
                a.pop(j)
                b.pop(j)
            elif b[j] == room[i]:
                if cage[a[j]] == None:
                    cage[a[j]] = b[j]
                nroom.append(a[j])
                a.pop(j)
                b.pop(j)
            else:
                j += 1
    print(cage, room,nroom,a)
    if (len(a) == 0 and None in cage.values()) or room == nroom:
        print('No')
        break
    room = nroom[:]
    nroom.clear()
else:
    print('Yes')
    for i in range (2,n+1):
        print(cage[i])

Buggy submission (verdict: Runtime Error):
import sys
n,m = map(int, sys.stdin.readline().rstrip("\n").split())
cage = {}
for i in range (2,n+1):
    cage[i] = None
ab = [map(int, line.rstrip("\n").split()) for line in sys.stdin]
a,b = [list(i) for i in zip(*ab)]
room = [1]
nroom = []
while None in cage.values():
    for i in range(len(room)):
        j = 0
        while j < (len(a)):
            if a[j] == room[i]:
                if cage[b[j]] == None:
                    cage[b[j]] = a[j]
                nroom.append(b[j])
                a.pop(j)
                b.pop(j)
                j += 1
            elif b[j] == room[i]:
                if cage[a[j]] == None:
                    cage[a[j]] = b[j]
                nroom.append(a[j])
                a.pop(j)
                b.pop(j)
                j += 1
            else:
                j += 1
    room = nroom
    if len(a) == 0 and None in cage.values():
        print('No')
        break
else:
    print('Yes')
    for i in range (2,n+1):
        print(cage[i])