qyliang/CodeNanoFix huggingface dataset:
Buggy code:
n=int(input())
words=[input() for idx in range(n)]

if len(list(set(words))) != len(words):
  print('No')
  exit()

if any(map(lambda a,b: a[-1]==b[0], words[:-1],words[1:])):
  print('No')
  exit()

print('Yes')

Fixed code:
n=int(input())
words=[input() for idx in range(n)]

if len(list(set(words))) != len(words):
  print('No')
  exit()

if all(map(lambda a,b: a[-1]==b[0], words[:-1],words[1:])):
  print('Yes')
else:
  print('No')
Buggy code:
n=int(input())
s=[input()for _ in[0]*n]
f=0
for i in range(1,n):
    f+=s[i-1][-1]!=s[i][0]
print("No"if len(set(s))<n else"Yes")


Fixed code:
n=int(input())
s=[input()for _ in[0]*n]
f=0
for i in range(1,n):
    f+=s[i-1][-1]!=s[i][0]
print("No"if f or len(set(s))<n else"Yes")
Buggy code:
N = int(input())
S = []
for i in range(N):
    S.append(input())



www = "YYY"
for i in range(N-2):

    if S[i][-1] != S[i+1][0]:
        www = "fuck"


qqq = "ZZZ"
S.sort()
for i in range(N-2):
    if S[i] == S[i+1]:
        qqq = "bich"

if www == "YYY" and qqq == "ZZZ":
    print("Yes")
else:
    print("No")


Fixed code:
N = int(input())
S = []
for i in range(N):
    S.append(input())



www = "YYY"
for i in range(N-1):
    if S[i][-1] != S[i+1][0]:
        www = "fuck"

qqq = "ZZZ"
S.sort()
for i in range(N-1):
    if S[i] == S[i+1]:
        qqq = "bich"

if www == "YYY" and qqq == "ZZZ":
    print("Yes")
else:
    print("No")
Buggy code:
n=int(input())
word=[]
for i in range(n):
  if i==0:
    word.append(input())
    continue
  k=input()
  if k in word:
    print("No")
    exit()
  a=list(word[-1])
  b=list(k)
  if a[-1]==b[0]:
    pass
  else:
    print("No")
    exit()
print("Yes")

Fixed code:
n=int(input())
word=[]
for i in range(n):
  if i==0:
    word.append(input())
    continue
  k=input()
  if k in word:
    print("No")
    exit()
  a=list(word[-1])
  b=list(k)
  word.append(k)
  if a[-1]==b[0]:
    pass
  else:
    print("No")
    exit()
print("Yes")
Buggy code:
n=int(input())
li=[]
for i in range(0,n):
    n=input()
    li.append(n)
flag=0
chck=1
temp=li[0]
for j in li:
    t=li.count(j)
    if(t>1):
        flag=1
        break
    if(chck!=1):
        p=len(temp)
        ch=temp[p-1]
        
        ch1=j[0]
        if(ch==ch1):
            flag=0
            temp=j
        else:
            flag=1
            break
    chck=chck+1
if(flag==1):
    print('NO')
else:
    print('YES')

Fixed code:
n=int(input())
li=[]
for i in range(0,n):
    n=input()
    li.append(n)
flag=0
chck=1
temp=li[0]
for j in li:
    t=li.count(j)
    if(t>1):
        flag=1
        break
    if(chck!=1):
        p=len(temp)
        ch=temp[p-1]
        
        ch1=j[0]
        if(ch==ch1):
            flag=0
            temp=j
        else:
            flag=1
            break
    chck=chck+1
if(flag==1):
    print('No')
else:
    print('Yes')
Buggy code:
def count_word(words, word):
    count = 0

    for w in words:
        if w == word:
            count += 1

    return count

n = int(input())

words = []
for i in range(n):
    words.append(input())

bind_letter = ""
for word in words:
    matches = count_word(words, word)
    if matches >= 2:
        print("No")
        exit()

    if bind_letter != "":
        if word[0] != bind_letter:
            print("No")
            exit()
    bind_letter = word[len(word) - 1]
    
p

Fixed code:
def count_word(words, word):
    count = 0

    for w in words:
        if w == word:
            count += 1

    return count

n = int(input())

words = []
for i in range(n):
    words.append(input())

bind_letter = ""
for word in words:
    matches = count_word(words, word)
    if matches >= 2:
        print("No")
        exit()

    if bind_letter != "":
        if word[0] != bind_letter:
            print("No")
            exit()
    bind_letter = word[len(word) - 1]
    
print("Yes")
Buggy code:
def resolve():
	n = int(input())
	ws = [input() for _ in range(n)]
	cnt = []
	for w in ws:
		if w in cnt:
			print('No')
			return
		if len(cnt) and cnt[0][-1] != w[-1]:
			print('No')
			return
	print('Yes')
resolve()

Fixed code:
def resolve():
	n = int(input())
	ws = [input() for _ in range(n)]
	cnt = []
	for w in ws:
		if w in cnt:
			print('No')
			return
		if len(cnt) and cnt[-1][-1] != w[0]:
			print('No')
			return
		cnt.append(w)
	print('Yes')
resolve()
Buggy code:
N = int(input())
A = [input() for _ in range(N)]
pre = A[0]
for a in A[1:]:
  if A.count(pre) >= 2:
    print("No")
    exit()
  if pre[-1] == a[0]:
    pre = a
print("Yes")    

Fixed code:
N = int(input())
A = [input() for _ in range(N)]
pre = A[0]
for a in A[1:]:
  if A.count(pre) >= 2:
    print("No")
    exit()
  if pre[-1] == a[0]:
    pre = a
  else:
    print("No")
    exit()
print("Yes")
Buggy code:
n = int(input())
w = [input() for i in range(n)]
ans = True
for j in range(1, n):
    if w[j][-1] != w[j-1][0]:
        ans = False
for k in range(n):
    for l in range(n):
        if l != k:
            if w[l] == w[k]:
                ans = False
        else:
            continue
if ans == True:
    print("Yes")
else:
    print("No")


Fixed code:
n = int(input())
w = [input() for i in range(n)]
ans = True
for j in range(n-1):
    if w[j][-1] != w[j+1][0]:
        ans = False
for k in range(n):
    for l in range(n):
        if l != k:
            if w[l] == w[k]:
                ans = False
        else:
            continue
if ans == True:
    print("Yes")
else:
    print("No")
Buggy code:
n=int(input())
l=[input()]
for i in range(n-1):
    w=input()
    if l[-1][-1]!=w[0] or w in l:
        print("No")
        break
else:print("Yes")

Fixed code:
n=int(input())
l=[input()]
for i in range(n-1):
    w=input()
    if l[-1][-1]!=w[0] or w in l:
        print("No")
        break
    l.append(w)
else:print("Yes")
Buggy code:
n = int(input())
w = [input() for i in range(n)]

s = set(w[0])
word = w[0][-1]

for i in range(1, n):
    if w[i] in s:
        print("No")
        exit()
    if w[i][0] == word:
        print("No")
        exit()
    s.add(w[i])
    word = w[i][-1]

print("Yes")

Fixed code:
n = int(input())
w = [input() for i in range(n)]

s = set([])
s.add(w[0])
word = w[0][-1]

for i in range(1, n):
    if w[i] in s:
        print("No")
        exit()
    if w[i][0] != word:
        print("No")
        exit()
    s.add(w[i])
    word = w[i][-1]

print("Yes")
Buggy code:
num_word = int(input())
word_list = []
flag = True

for i in range(num_word):
    word_list.append(input())

for j in range(num_word - 1):
    word1 = word_list[j]
    word2 = word_list[j + 1]
    if word1[len(word1) - 1] != word2[0]:
        flag = False
        break

if flag:
    print("Yes")
else:
    print("No")

Fixed code:
num_word = int(input())
word_list = []
flag = True

for i in range(num_word):
    word_list.append(input())

for j in range(num_word - 1):
    word1 = word_list[j]
    word2 = word_list[j + 1]
    for k in range(j):
        if word1 == word_list[k]:
            flag = False
            break
    if word1[len(word1) - 1] != word2[0]:
        flag = False
        break
for l in range(num_word  - 1):
    if word_list[num_word - 1] == word_list[l]:
        flag = False

if flag:
    print("Yes")
else:
    print("No")
Buggy code:
n = int(input())
list = [input() for _ in range(n)]
a = 'Yes'
if len(set(list))!=n:
    ans = 'No'
for i in range(n-1):
    if list[i][-1]!=list[i+1][0]:
        a = 'No'
print(a)

Fixed code:
n = int(input())
list = [input() for _ in range(n)]
a = 'Yes'
if len(set(list))!=n:
    a = 'No'
for i in range(n-1):
    if list[i][-1]!=list[i+1][0]:
        a = 'No'
print(a)
Buggy code:
N=int(input())
L=[]
count=0
for i in range (N):
	L.append(int(input()))
if len(set(L))!=N:
	print("No")
else:
	for i in range (N-1):
		if L[i][-1]!=L[i+1][0]:
			count+=1
	if count==0:
		print("Yes")
	else:
		print("No")

Fixed code:
N=int(input())
L=[]
count=0
for i in range (N):
	L.append(input())
if len(set(L))!=N:
	print("No")
else:
	for i in range (N-1):
		if L[i][-1]!=L[i+1][0]:
			count+=1
	if count==0:
		print("Yes")
	else:
		print("No")
Buggy code:
N = int(input())
word = [input() for _ in range(N)]
s = set(word)
if len(s) != N:
  print('No')
  exit
ok = True
for i in range(1,N):
  if word[i][0] != word[i-1][-1] :
    ok = False
print('Yes' if ok else 'No')


Fixed code:
N = int(input())
word = [input() for _ in range(N)]
s = set(word)
ok = True
if len(s) != N:
    ok = False
for i in range(1,N):
  if word[i][0] != word[i-1][-1] :
    ok = False
print('Yes' if ok else 'No')
Buggy code:
n = int(input())
list_w = [input() for s in range(0, n)]
for i in range(0, n):
    if i == 0 or (list_w[i][-1] == list_w[i][0] and list_w[i] in list_w[:i]):
        continue
    else:
        print("No")
        exit()
print("Yes")

Fixed code:
n = int(input())
list_w = [input() for s in range(0, n)]
for i in range(0, n):
    if i == 0 or (list_w[i - 1][-1] == list_w[i][0]) and list_w[i] not in list_w[:i]:
        continue
    else:
        print("No")
        exit()
print("Yes")
Buggy code:
n = int(input())
word_list = []
flag = True
for i in range(n):
    word = input()
    if word_list == []:
        word_list.append(word)
    else:
        if word_list[-1][-1] == word[0]:
            word_list.append(word)
        else:
            flag = False
            break
            
if flag:
    print('Yes')
else:
    print('No')

Fixed code:
n = int(input())
word_list = []
flag = True
for i in range(n):
    word = input()
    if word_list == []:
        word_list.append(word)
    else:
        if (word_list[-1][-1] == word[0]) and (word not in word_list):
            word_list.append(word)
        else:
            flag = False
            break
            
if flag:
    print('Yes')
else:
    print('No')
Buggy code:
n=int(input())
w=[input() for i in range(n)]
last=""
wl=[]
ans="Yes"
for x,i in enumerate(w):
    if x==0:
        last=i[-1]
        continue
    if i in wl:
        ans="No"
    if i[0]!=last:
        ans="No"
    last=i[-1]
    wl.append(i)
print(ans)

Fixed code:
n=int(input())
w=[input() for i in range(n)]
last=""
wl=[]
ans="Yes"
for x,i in enumerate(w):
    if x==0:
        last=i[-1]
        wl.append(i)
        continue
    if i in wl:
        ans="No"
    if i[0]!=last:
        ans="No"
    last=i[-1]
    wl.append(i)
print(ans)
Buggy code:
import collecions

N = int(input())
W = [input() for i in range(N)]
c = collecions.Counter(W)

for i in range(N-1):
    if W[i][-1] != W[i+1][1]:
        print("No")
        exit()
if len(c) != N:
    print("No")
    exit()
print("Yes")

Fixed code:
import collections

N = int(input())
W = [input() for i in range(N)]
c = collections.Counter(W)

for i in range(N-1):
    if W[i][-1] != W[i+1][0]:
        print("No")
        exit()
if len(c) != N:
    print("No")
    exit()
print("Yes")
Buggy code:
n=int(input())
a=input()
b=a[len(a)-1]
word1=[a]
word2=[b]
c=0

for i in range(n-1):
    aa=input()
    bb=aa[0]
    if aa not in word1 and word2[i]==bb:
        word1.append(aa)
        top=aa[len(aa)-1]
        word2.append(top)
    else:
        c=1
        
print("Yes" if c==0 else "No")

Fixed code:
n=int(input())
a=input()
b=a[len(a)-1]
word1=[a]
word2=[b]
c=0

for i in range(n-1):
    aa=input()
    bb=aa[0]
    if aa not in word1 and word2[i]==bb:
        word1.append(aa)
        top=aa[len(aa)-1]
        word2.append(top)
    else:
        c=1
        break
        
print("Yes" if c==0 else "No")
Buggy code:
n,w=int(input()),[input()for i in range(n)]
def sortex(X):
  b=sorted(X)
  b.append("null")
  a=[]
  for i in range(len(X)):
    if b[i]!=b[i+1]:a.append(b[i])
  return a
if len(w)!=len(sortex(w)):
  print("No")
  exit()
for i in range(len(w)-1):
  if w[i][-1]!=w[i+1][0]:
    print("No")
    exit()
print("Yes")

Fixed code:
n=int(input());w=[input()for i in range(n)]
def sortex(X):
  b=sorted(X)
  b.append("null")
  a=[]
  for i in range(len(X)):
    if b[i]!=b[i+1]:a.append(b[i])
  return a
if len(w)!=len(sortex(w)):
  print("No")
  exit()
for i in range(len(w)-1):
  if w[i][-1]!=w[i+1][0]:
    print("No")
    exit()
print("Yes")
Buggy code:
N=int(input())
last = input()
wds = set([last])
for i in range(N-1):
    print(i)
    wd = input()
    if wd in wds or last[-1]!=wd[0]: 
        print('No')
        break
    last = wd
    wds.add(wd)
print('Yes')

Fixed code:
N=int(input())
last = input()
wds = set([last])
res = "Yes"
for i in range(N-1):
    wd = input()
    if wd in wds or last[-1]!=wd[0]: 
        res = "No"
        break
    last = wd
    wds.add(wd)
print(res)
Buggy code:
N = int(input())
w_list = []
for i in range(N):
    w_list.append(str(input()))

ans = 0

if len(set(w_list)) != N:
    print('No')
    exit()
for i in range(1,N):
    print(i)
    if w_list[i-1][-1] == w_list[i][0]:
        ans += 1
if ans == N - 1:
    print('Yes')
else:
    print('No')

Fixed code:
N = int(input())
w_list = []
for i in range(N):
    w_list.append(str(input()))

ans = 0

if len(set(w_list)) != N:
    print('No')
    exit()
for i in range(1,N):
    if w_list[i-1][-1] == w_list[i][0]:
        ans += 1
if ans == N - 1:
    print('Yes')
else:
    print('No')
Buggy code:
n=[input() for _ in range(int(input()))];if len(set(n))!=len(n): print('No');exit()
print('NYoe s'[all([1 if n[i-1][-1]==n[i][0] else 0 for i in range(1,len(n))])::2])

Fixed code:
n=[input() for _ in range(int(input()))]
if len(set(n))!=len(n): print('No');exit()
print('NYoe s'[all([1 if n[i-1][-1]==n[i][0] else 0 for i in range(1,len(n))])::2])
Buggy code:
N=int(input())

W=[input() for i in range(N)]

check=1

for i in range(2,N):
    if W[i-1][-1] != W[i][0]:
        check=0

    




W.sort()



for i in range(2,N):
    if W[i]==W[i-1]:
        check=0
        print(i)






if check==1:
    print("Yes")

else:
    print("No")


Fixed code:
N=int(input())

W=[input() for i in range(N)]

check=1

for i in range(1,N):
    if W[i-1][-1] != W[i][0]:
        check=0

W.sort()


for i in range(2,N):
    if W[i]==W[i-1]:
        check=0

if check==1:
    print("Yes")

else:
    print("No")
Buggy code:
def is_unique(seq):
    return len(seq) == len(set(seq))

N = int(input())
words = []
for i in range(N):
    words.append(input())
hantei = 0
for i in range(N-1):
    a = [x for x in words[i]]
    b = [x for x in words[i+1]]
    if a[len(a)-1] == b[1]:
        pass
    else:
        hantei += 1
        break
if hantei == 0 and is_unique(words) == True:
    print("Yes")
else:
    print("No")


Fixed code:
def is_unique(seq):
    return len(seq) == len(set(seq))

N = int(input())
words = []
for i in range(N):
    words.append(input())
hantei = 0
for i in range(N-1):
    a = [x for x in words[i]]
    b = [x for x in words[i+1]]
    if a[len(a)-1] == b[0]:
        pass
    else:
        hantei += 1
        break
if hantei == 0 and is_unique(words) == True:
    print("Yes")
else:
    print("No")
Buggy code:
W = []
judge = True
a = ""
N = int(input())
for i in range(N):
    s = input()
    W.append(s)
    if i == 0:
        a = s[len(s)-1]
    else:
        if a != s[0] or s in W:
            judge = False
            break
        else:
            a = s[len(s)-1]
if judge:
    print("Yes"):
else:
    print("No")

Fixed code:
W = []
judge = True
a = ""
N = int(input())
for i in range(N):
    s = input()
    if i == 0:
        a = s[len(s)-1]
    else:
        if a != s[0] or s in W:
            judge = False
            break
        else:
            a = s[len(s)-1]
    W.append(s)
if judge:
    print("Yes")
else:
    print("No")
Buggy code:
n = int(input())

words = {}
w = ''
ok = True
for i in range(n):
  nw = input()
  if nw in words:
    ok = False
    break
  words.add(w)
  if w and w[-1] != nw[0]:
    ok = False
  w = nw

if ok:
  print('Yes')
else:
  print('No')


Fixed code:
n = int(input())

words = set()
w = ''
ok = True
for i in range(n):
  nw = input()
  if nw in words:
    ok = False
    break
  words.add(w)
  if w and w[-1] != nw[0]:
    ok = False
  w = nw

if ok:
  print('Yes')
else:
  print('No')
Buggy code:
n=int(input())
W=[input() for i in range(n)]
cnt=0
for i in range(1,n):
    if W[i-1][-1]==W[i][0]:
        cnt+=1
if cnt==n-1:
    print("Yes")
else:
    print("No")


Fixed code:
n=int(input())
W=[input() for i in range(n)]
cnt=0
for i in range(1,n):
    if W[i-1][-1]==W[i][0] and W[i] not in W[:i]:
        cnt+=1
if cnt==n-1:
    print("Yes")
else:
    print("No")
Buggy code:
N = int(input())
li = []
w = input()
li.append(w)
k = 0
ans = "Yes"
for i in range(N) :
    word = input()
    for j in range(len(li)) :
        if li[j] == word :
            k = 1
            break
    last_word = li[-1]
    if last_word[-1] != word[0] :
        k = 1
    if k == 1 :
        ans = "No"
        break
    li.append(word)
print(ans)

Fixed code:
N = int(input())
li = []
w = input()
li.append(w)
k = 0
ans = "Yes"
for i in range(N-1) :
    word = input()
    for j in range(len(li)) :
        if li[j] == word :
            k = 1
            break
    last_word = li[-1]
    if last_word[-1] != word[0] :
        k = 1
    if k == 1 :
        ans = "No"
        break
    li.append(word)
print(ans)
Buggy code:
n=int(input())
w=[input() for i in range(n)]    
count=0
if len(set(w))<len(w):
    print('No')
else:
    for i in range(n-1):
        if w[i][-1]==w[i+1][0]:
            count+=1
    if count==n-1:
        print('Yes')
    else:
        print('No')
print(count)

Fixed code:
n=int(input())
w=[input() for i in range(n)]    
count=0
if len(set(w))<len(w):
    print('No')
else:
    for i in range(n-1):
        if w[i][-1]==w[i+1][0]:
            count+=1
    if count==n-1:
        print('Yes')
    else:
        print('No')
Buggy code:
N = int(input())
w = input()
W_list = [w]
for i in range(N-1):
  W = input()
  if w[-1] == W[0] and W not in W.list:
    W_list.append(w)
    w = W
  else:
    print("No")
    exit()
print("Yes")

Fixed code:
N = int(input())
w = input()
W_list = [w]
for i in range(N-1):
  W = input()
  if w[-1] == W[0] and W not in W_list:
    W_list.append(w)
    w = W
  else:
    print("No")
    exit()
print("Yes")
Buggy code:
n = int(input())
w = [input() for _ in range(n)]
res = True
for i in range(1,n):
    print(w[i-1][-1])
    print(w[i][0])
    print(w[i][0] == w[i-1][-1])
    if w[i][0] != w[i-1][-1]:
        res = False
    else:
        continue
if res == True and len(w) == len(set(w)):
    print("Yes")
else:
    print("No")

Fixed code:
n = int(input())
w = [input() for _ in range(n)]
res = True
for i in range(1,n):
    if w[i][0] != w[i-1][-1]:
        res = False
    else:
        continue
if res == True and len(w) == len(set(w)):
    print("Yes")
else:
    print("No")
Buggy code:
n=int(input())
B=[]
S = 0
for i in range(0,n):
    B.append((input()))
C = set(B)
if len(B) != len(C):
    print("No")
else:
    for m in range(n-1):
        if B[m][-1] == B[m+1][0]:
            S += 1
        if S == n-1:
            print("Yes")
        else: 
            print("No")

Fixed code:
n=int(input())
B=[]
S = 0
for i in range(0,n):
    B.append((input()))
C = set(B)
if len(B) != len(C):
    print("No")
else:
    for m in range(n-1):
        if B[m][-1] == B[m+1][0]:
            S += 1
    if S == n-1:
        print("Yes")
    else: 
        print("No")
Buggy code:
n = int(input())
l = [input() for _ in [0]*n]

if len(set(l)) != n:
    print('No')
else:
    for i in range(n-1):
        #print(i)
        #print(list(l[i])[-1])
        #print(list(l[i+1])[0])
        if list(l[i])[-1] == list(l[i+1][0]):
            print('No')
            break
        else:
            continue
    else:
        print('Yes')


Fixed code:
n = int(input())
l = [input() for _ in [0]*n]
#print(l)
if len(set(l)) != n:
    print('No')
else:
    for i in range(n-1):
        #print(i)
        #print(list(l[i])[-1])
        #print(list(l[i+1])[0])
        if l[i][-1] != l[i+1][0]:
            print('No')
            break
        #else:
            #print('Noo')
            #break
        else:
            continue
    else:
        print('Yes')
Buggy code:
from sys import exit
n=int(input())
s=input()
w=[]
w.append(s)
for i in range(n-1):
  s=input()
  if w[i][-1]!=a[0] or s in w:
    print('No')
    exit()
  else:
    w.append(s)
print('Yes')
  

Fixed code:
from sys import exit
n=int(input())
s=input()
w=[]
w.append(s)
for i in range(n-1):
  s=input()
  if w[i][-1]!=s[0] or s in w:
    print('No')
    exit()
  else:
    w.append(s)
print('Yes')
Buggy code:
# -*- coding:utf-8 -*-

if __name__ == "__main__":
    N = int(input())
    pre_w = input()
    words = [pre_w]
    for i in range(N-1):
        w = input()
        if w in words:
            print("No")
            exit()
        words.append(w)

        if pre_w[-1] == w[0]:
            continue
        else:
            print("No")
            exit()
    print("Yes")


Fixed code:
# -*- coding:utf-8 -*-

if __name__ == "__main__":
    N = int(input())
    pre_w = input()
    words = [pre_w]
    for i in range(N-1):
        w = input()
        if w in words:
            print("No")
            exit()
        words.append(w)

        if pre_w[-1] == w[0]:
            pre_w = w
            continue
        else:
            print("No")
            exit()
    print("Yes")
Buggy code:
N = int(input())
W = [input() for i in range(N)]

memo = [W[0]]
OK = True
pre = W[0]
for word in W[1:]:
    if word in memo or pre[-1] != word[0]:
        OK = False
        print("No")
        break
    pre = word
if OK:
    print("Yes")

Fixed code:
N = int(input())
W = [input() for i in range(N)]

memo = [W[0]]
OK = True
pre = W[0]
for word in W[1:]:
    if word in memo or pre[-1] != word[0]:
        OK = False
        print("No")
        break
    memo.append(word)
    pre = word
if OK:
    print("Yes")
Buggy code:
if __name__ == '__main__':
  
  flag = 1
  
  wordNum = int(input())
  wordAll = []

  for i in range(wordNum) :

    word = input()
    wordAll.append(word)
    wordLen = len(word)
    
    if i > 0 and wordLast != word[0]:
      flag = 0
      break
    
    for j in range(len(wordAll)):
      if wordAll[j] == word:
        flag == 0
        break
    
    wordLast = word[wordLen - 1]

  if flag == 1 :
    print("Yes")
    
  else :
    print("No")

Fixed code:
if __name__ == '__main__':
  
  flag = 1
  
  wordNum = int(input())
  wordAll = []

  for i in range(wordNum) :

    word = input()
    wordAll.append(word)
    wordLen = len(word)
    
    if i > 0 and wordLast != word[0]:
      flag = 0
      break
    
    
    for j in range(len(wordAll)-1):
      if wordAll[j] == word:
        flag = 0
        break
    
    
    wordLast = word[wordLen - 1]

    
  if flag == 1 :
    print("Yes")
    
  else :
    print("No")
Buggy code:
#https://atcoder.jp/contests/abc109/tasks/abc109_b
import collections
N = int(input())
Word_List = []
SP = ""
for i in range(N):
    CW = str(input())
    if i == 0:
        Word_List.append(CW)
        SP = CW[-1]
    elif SP != CW[0]:
        break
    else:
        Word_List.append(CW)
        SP = CW[-1]
else:
    Word_List = collections.Counter(Word_List))
    if len(Word_List) != N:
        print("No")
    else:
        print("Yes")

Fixed code:
#https://atcoder.jp/contests/abc109/tasks/abc109_b
import collections
N = int(input())
Word_List = []
SP = ""
for i in range(N):
    CW = str(input())
    if i == 0:
        Word_List.append(CW)
        SP = CW[-1]
    elif SP != CW[0]:
        print("No")
        break
    else:
        Word_List.append(CW)
        SP = CW[-1]
else:
    Word_List = collections.Counter(Word_List)
    if len(Word_List) != N:
        print("No")
    else:
        print("Yes")
Buggy code:
N = int(input())
W = [input() for _ in range(N)]

a = []
pre = W[0]
flag = False
for wi in W[1:]:
    if wi in a or pre[-1] != wi[0]:
        flag = True
        break
        
if flag:
    print('No')
else:
    print('Yes')

Fixed code:
N = int(input())
W = [input() for _ in range(N)]

a = []
pre = W[0]
a.append(pre)
flag = False
for wi in W[1:]:
    if wi in a or pre[-1] != wi[0]:
        flag = True
        break
    pre = wi
    a.append(wi)
        
if flag:
    print('No')
else:
    print('Yes')