Buggy python submission (verdict: Runtime Error):
import itertools
import sys
N,M=map(int,input().split())
dic={}
for _ in range(N):
    a,b=map(int,input().split())
    if(a in dic.keys()):
        if((b in dic[a])==False):
            dic[a].append(b)
    else:
        dic[a]=[b]
    if(b in dic.keys()):
        if((a in dic.values())==False):
            dic[b].append(a)
    else:
        dic[b]=[a]

if(M==0):
    print(0)
    sys.exit()

node=[i for i in range(N)]
ans=0
strokes=itertools.permutations(node,M)

def judge(A,B):
    values=dic[A]
    if(B in values):
        return True
    else:
        return False

for stroke in strokes:
    stroke=list(stroke)
    if(stroke[0]==0):
        pre=stroke.pop(0) + 1
        for s in stroke:
            if(judge(pre,s+1)==False):
                break
            pre=s+1
        else:
            ans+=1
    
print(ans)


Fixed submission:
N, M = map(int, input().split())
G = [[] for i in range(N)]
for i in range(M):
    a, b = map(int, input().split())
    G[a - 1].append(b - 1)
    G[b - 1].append(a - 1)
cnt = [0]
def dfs(V, s):
    V[s] = 1
    if sum(V) == N:
        cnt[0] += 1                    
    else:
        for adj in G[s]:
            if V[adj] == 0:             
                dfs(V[:adj] + [1] + V[adj + 1:], adj)  #ここで分岐がたくさん発生する
dfs([0] * N, 0)
print(cnt[0])

Buggy python submission (verdict: Runtime Error):
import itertools
import sys
N,M=map(int,input().split())
dic={}
for _ in range(N):
    a,b=map(int,input().split())
    if(a in dic.keys()):
        dic[a].append(b)
    else:
        dic[a]=[b]
    if(b in dic.keys()):
        dic[b].append(a)
    else:
        dic[b]=[a]


if(M==0):
    print(0)
    sys.exit()
    
node=[i for i in range(N)]
ans=0
strokes=itertools.permutations(node,M)

def judge(A,B):
    values=dic[A]
    if(B in values):
        return True
    else:
        return False

for stroke in strokes:
    stroke=list(stroke)
    if(stroke[0]==0):
        pre=stroke.pop(0) + 1
        for s in stroke:
            if(judge(pre,s+1)==False):
                break
            pre=s+1
        else:
            ans+=1
    
print(ans)

Fixed submission:
N, M = map(int, input().split())
G = [[] for i in range(N)]
for i in range(M):
    a, b = map(int, input().split())
    G[a - 1].append(b - 1)
    G[b - 1].append(a - 1)
cnt = [0]
def dfs(V, s):
    V[s] = 1
    if sum(V) == N:
        cnt[0] += 1                    
    else:
        for adj in G[s]:
            if V[adj] == 0:             
                dfs(V[:adj] + [1] + V[adj + 1:], adj)  #ここで分岐がたくさん発生する
dfs([0] * N, 0)
print(cnt[0])

Buggy python submission (verdict: Runtime Error):
import itertools
N,M=map(int,input().split())
dic={}
for _ in range(N):
    a,b=map(int,input().split())
    if(a in dic.keys()):
        dic[a].append(b)
    else:
        dic[a]=[b]
    if(b in dic.keys()):
        dic[b].append(a)
    else:
        dic[b]=[a]
        
node=[i for i in range(N)]
ans=0
strokes=itertools.permutations(node,M)

def judge(A,B):
    values=dic[A]
    if(B in values):
        return True
    else:
        return False

for stroke in strokes:
    stroke=list(stroke)
    if(stroke[0]==0):
        pre=stroke.pop(0) + 1
        for s in stroke:
            if(judge(pre,s+1)==False):
                break
            pre=s+1
        else:
            ans+=1
    
print(ans)

Fixed submission:
N, M = map(int, input().split())
G = [[] for i in range(N)]
for i in range(M):
    a, b = map(int, input().split())
    G[a - 1].append(b - 1)
    G[b - 1].append(a - 1)
cnt = [0]
def dfs(V, s):
    V[s] = 1
    if sum(V) == N:
        cnt[0] += 1                    
    else:
        for adj in G[s]:
            if V[adj] == 0:             
                dfs(V[:adj] + [1] + V[adj + 1:], adj)  #ここで分岐がたくさん発生する
dfs([0] * N, 0)
print(cnt[0])

Buggy python submission (verdict: Runtime Error):
def df_search(searchNode,node,sss,i):
    global cnt
    ss=sss+1
    sn=searchNode
    sn.append(i)
    if(hantei==sorted(sn)):
        if(ans==[]):
            cnt+=1
            ans.append(searchNode)
        else:
            for an in ans[:]:
                if(an != searchNode):
                    cnt+=1
                    ans.append(searchNode)
    for i in node:
        if(i not in sn):
            df_search(sn[:],df_dic[i],ss,i)

ans=[]
lis=[]
df_dic=dict()

NODES,EDGE=map(int,input().split())
df_flag = [0 for i in range(NODES)]  # 探索状況[0:未探索, 1:探索済み] 初期値：0
for i in range(EDGE):
    lis.append(list(map(int,input().split())))
    df_dic[i+1]=[]
for i in lis:
    df_dic[i[0]].append(i[1])
    df_dic[i[1]].append(i[0])
cnt=0
hantei=[i for i in range(1,EDGE+1)]
df_search([],df_dic[1],0,1)
print(cnt)

Fixed submission:
N, M = map(int, input().split())
G = [[] for i in range(N)]
for i in range(M):
    a, b = map(int, input().split())
    G[a - 1].append(b - 1)
    G[b - 1].append(a - 1)
cnt = [0]
def dfs(V, s):
    V[s] = 1
    if sum(V) == N:
        cnt[0] += 1                    
    else:
        for adj in G[s]:
            if V[adj] == 0:             
                dfs(V[:adj] + [1] + V[adj + 1:], adj)  #ここで分岐がたくさん発生する
dfs([0] * N, 0)
print(cnt[0])