qyliang/CodeNanoFix huggingface dataset:
Buggy code:
def main():
    N = int(input())
    word_list=[input() for i in range(N)]
    already_list = []
    for i, word in enumerate(word_list):
        if(i==0):
            already_list.append(word)
            continue
        if(word not in already_list and word[0] == word_list[i-1][0]):
            already_list.append(word)
        else:
            print('No')
            return
    print('Yes')




if __name__ == "__main__":
    main()

Fixed code:
def main():
    N = int(input())
    word_list=[input() for i in range(N)]
    already_list = []
    for i, word in enumerate(word_list):
        if(i==0):
            already_list.append(word)
            continue
        if(word not in already_list and word[0] == word_list[i-1][len(word_list[i-1])-1]):
            already_list.append(word)
        else:
            print('No')
            return
    print('Yes')




if __name__ == "__main__":
    main()
Buggy code:
def si():

    n = int(input()) 
    tk = [input() for i in range(n)]
    tu = len(set(tk))
    l =[]
    k = []

 
        
    oo = 0


    while oo < tu:
        t = tk[oo]
        l.append(t[0])
        k.append(t[-1])
        oo += 1
        
    oo = 0


    while oo < tu-1:
        if k[oo] != l[oo+1]:
            return False
        
        oo += 1


    if tu != n:
        print(tu)
        print(n)
        
        return False
    
    return True
    
if si():
    print("Yes")
else:
    print("No")

Fixed code:
def si():

    n = int(input()) 
    tk = [input() for i in range(n)]
    tu = len(set(tk))
    l =[]
    k = []

 
        
    oo = 0


    while oo < tu:
        t = tk[oo]
        l.append(t[0])
        k.append(t[-1])
        oo += 1
        
    oo = 0


    while oo < tu-1:
        if k[oo] != l[oo+1]:
            return False
        
        oo += 1


    if tu != n:
        return False
    
    return True
    
if si():
    print("Yes")
else:
    print("No")
Buggy code:
import sys
input = sys.stdin.readline
N = int(input())
W = [input() for i in range(N)]
s = set(W)
flag = False
if len(s) != N:
    print("No")
else:
    for i in range(N-1):
        if W[i][-1] != W[i+1][0]:
            flag = True
            break
if flag:
    print("No")
else:
    print("Yes")

Fixed code:
import sys
input = sys.stdin.readline
N = int(input())
W = [input().strip() for i in range(N)]
s = set(W)
flag = False
if len(list(s)) != N:
    print("No")
else:
    for i in range(N-1):
        if W[i][-1] != W[i+1][0]:
            flag = True
            break
    if flag:
        print("No")
    else:
        print("Yes")
Buggy code:
import collections
n = int(input())
k = []
result=[]
for i in range(n):
    a = input()
    k.append(a)
ans = collections.Counter(k)
for i in range(1,n):
    if k[i-1][-1] == k[i][0] and ans.most_common()[0][1] == 1:
        result.append("1")
    else:
        result.append("0")
print(result)
aim = collections.Counter(result)
print(aim.most_common()[0][1])
if aim.most_common()[0][1] != n-1 or aim.most_common()[0][0] =='0':
    print('No')
else:
    print('Yes')

Fixed code:
import collections
n = int(input())
k = []
result=[]
for i in range(n):
    a = input()
    k.append(a)
ans = collections.Counter(k)
for i in range(1,n):
    if k[i-1][-1] == k[i][0] and ans.most_common()[0][1] == 1:
        result.append("1")
    else:
        result.append("0")
aim = collections.Counter(result)
if aim.most_common()[0][1] != n-1 or aim.most_common()[0][0] =='0':
    print('No')
else:
    print('Yes')
Buggy code:
n = int(input())
a = [input() for i in range(n)] 

for i in range(1, n):
  if a[i-1][-1]!=a[i][0] or a[i]==a[:i-1]:
    print('No')
    break
  else:
    print('Yes')

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

for i in range(1, n):
  if a[i-1][-1]!=a[i][0] or a[i] in a[:i-1]:
    print('No')
    break
else:
  print('Yes')
Buggy code:
n=int(input())
w=[input() for s in range(n)]
k=[]
D=0
for i in range(n):
 if w[i] in k or w[i-1][-1]!=w[i][0]:
  D+=1
 else:
  k.append(w[i])

if D>0:
 print("No")
else:
 print("Yes")

Fixed code:
n=int(input())
w=[input() for s in range(n)]
k=[w[0]]
D=0
for i in range(1,n):
 if w[i] in k or w[i-1][-1]!=w[i][0]:
  D+=1
 else:
  k.append(w[i])

if D>0:
 print("No")
else:
 print("Yes")
Buggy code:
n=int(input())
hoge=[]
no=0

a=input()
hoge.append(a)
saigo=a[-1]

for i in range(n-1):
  a=input()
  hoge.append(a)
  if(hoge.count(a)>1):
    no=1
    break
  if(saigo==a[-1]):
    no=1
    break
  saigo=a[-1]
  
if(no==0):
  print("Yes")
else:
  print("No")

Fixed code:
n=int(input())
hoge=[]
no=0

a=input()
hoge.append(a)
saigo=a[-1]

for i in range(n-1):
  a=input()
  hoge.append(a)
  if(hoge.count(a)>1):
    no=1
    break
  if(saigo==a[0]):
    saigo=a[-1]
  else:
    no=1
    break
  
if(no==0):
  print("Yes")
else:
  print("No")
Buggy code:
N = int(input())
a = [input() for i in range(N)]

if len(set(a)) != N:
    print("No")
    exit()

for i in range(1,N):
    if  a[i-1][-1] != a[i][0]:
        print("No")
        exit()
pront("Yes")


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

if len(set(a)) != N:
    print("No")
    exit()

for i in range(1,N):
    if  a[i-1][-1] != a[i][0]:
        print("No")
        exit()
print("Yes")
Buggy code:
N = int(input())
W = [list(input()) for _ in range(N)]
ans = 'Yes'
W_set = set(W)
if len(W) == len(W_set):
  for i in range(1, N - 1):
    if W[i][0] != W[i-1][-1]:
      ans = 'No'
      break
else:
  ans = 'No'
print(ans)

Fixed code:
N = int(input())
W = [input() for _ in range(N)]
ans = 'Yes'
W_set = set(W)
if len(W) == len(W_set):
  for i in range(1, N):
    if W[i][0] != W[i-1][-1]:
      ans = 'No'
      break
else:
  ans = 'No'
print(ans)
Buggy code:
N = int(input())
W = []
for i in range(N):
    W.append(input())
flag = True
for i in range(N-1):
    if W[i][-1] != W[i+1][0]:
        flag = False
        break
    for j in range(i+1):
        if W[i] == W[j]:
            flag = False
            break
print("Yes") if flag else print("No")

Fixed code:
N = int(input())
W = []
for i in range(N):
    W.append(input())
flag = True
for i in range(N-1):
    if W[i][-1] != W[i+1][0]:
        flag = False
        break
    for j in range(i):
        if W[i+1] == W[j]:
            flag = False
            break
print("Yes") if flag else print("No")
Buggy code:
import sys
 
n = int(input())
l = []
p = None
 
for i in range(n):
  s = input()
  if s in l and (p == None or p[-1:] == s[1:]):
    l.append(s)
    p = s
  else:
    print("No")
    sys.exit()
print("Yes")

Fixed code:
import sys
 
n = int(input())
l = []
p = None
 
for i in range(n):
  s = input()
  if s not in l and (p == None or p[-1:] == s[:1]):
    l.append(s)
    p = s
  else:
    print("No")
    sys.exit()
print("Yes")
Buggy code:
#B - Shiritori(ABC109)
N=int(input())
s=True
w1=input()
W=[w1]
for i in range(1,N):
    w2=input()
    W.append(w2)
    if len(set(W))<len(W) and w1[-1]==w2[0]:
        w1=w2
    else:
        s= False
if s:
    print("Yes")
else:
    print("No")

Fixed code:
#B - Shiritori(ABC109)
N=int(input())
s=True
w1=input()
W=[w1]
for i in range(N-1):
    w2=input()
    W.append(w2)
    if len(set(W))==len(W) and w1[-1]==w2[0]:
        w1=w2
    else:
        s= False
if s:
    print("Yes")
else:
    print("No")
Buggy code:
n = int(input()) 
a = [int(input()) for i in range(n)] 

used = [a[0]]
pre = a[0]
for i in a[1:]:
    if i not in used and pre[-1] == i[0]:
        used.append(i)
        pre = i
    else:
        print("No")
        exit()

print("Yes")

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

used = [a[0]]
pre = a[0]
for i in a[1:]:
    if i not in used and pre[-1] == i[0]:
        used.append(i)
        pre = i
    else:
        print("No")
        exit()

print("Yes")
Buggy code:
N = int(input())
w = []
for i in range(N):
    w.append(input())
    if i ==0:
        continue
    if w[i][0] !=  w[i-1][-1]:
        print('No')
        return

if N == len(set(w)):
    print('Yes')
else:
    

Fixed code:
def main():
    N = int(input())
    w = []
    for i in range(N):
        w.append(input())
        if i == 0:
            continue
        if w[i][0] != w[i-1][-1]:
            print('No')
            return

    if N == len(set(w)):
        print('Yes')
    else:
        print('No')

main()
Buggy code:
n = int(input())
a = [input() for i in range(n)]
b = []
b.append(a[0])
res = True
for i in range(1,n):
    if a[i-1][-1] != a[i][0]:
        res = False
        break
    if a[i] in b:
        res = False
        break
    b.append(a[i])

if res:
    print('Yes')
else:
    print('NO')

Fixed code:
n = int(input())
a = [input() for i in range(n)]
b = []
b.append(a[0])
res = True
for i in range(1,n):
    if a[i-1][-1] != a[i][0]:
        res = False
        break
    if a[i] in b:
        res = False
        break
    b.append(a[i])

if res:
    print('Yes')
else:
    print('No')
Buggy code:
N=int(input())
W=[]
for i in range(N):
    w=input()
    W.append(w)
last=W[0][-1]
S=set()
S.add(w[0])
for i in range(1,N):
    if W[i][0]==last and not W[i] in S:
        pass
    else:
        print("No")
        exit()
    S.add(W[i])
    last=W[i][-1]
print("Yes")

Fixed code:
N=int(input())
W=[]
for i in range(N):
    w=input()
    W.append(w)
last=W[0][-1]
S=set()
S.add(W[0])
for i in range(1,N):
    if W[i][0]==last and not W[i] in S:
        pass
    else:
        print("No")
        exit()
    S.add(W[i])
    last=W[i][-1]
print("Yes")
Buggy code:
from collections import defaultdict
n=int(input())
s=defaultdict(lambda: 0)
l=list([input() for i in range(n)])
f='Yes'
for v in l:
  s[v]+=1
  if s[v] >= 2:
    f='No'
print(f)


Fixed code:
from collections import defaultdict
n=int(input())
s=defaultdict(lambda: 0)
l=list([input() for i in range(n)])
f='Yes'
i=-1
for v in l:
  s[v]+=1
  if s[v] >= 2:
    f='No'
  if i!=-1 and l[i][-1] != v[0]:
    f='No'
  i+=1
print(f)
Buggy code:
n = int(input())
l = [input() for _ in range(n)]

if len(l) != len(set(l)):
    print('No')

flg = True
for i in range(len(l)-1):
    if l[i][-1] != l[i+1][0]:
        print('No')
        flg = False
        break

if flg:
    print('Yes')


Fixed code:
n = int(input())
l = [input() for _ in range(n)]

flg = True
if len(l) != len(set(l)):
    flg = False


for i in range(len(l)-1):
    if l[i][-1] != l[i+1][0]:
        flg = False
        break

print('Yes' if flg else 'No')
Buggy code:
n = int(input())
words =[]
words.append(input().rstrip())

for _ in range(1, n):
  s = input().rstrip()
  if s[0] != words[-1][-1] or s in words:
    print('No')
    break
else:
  print('Yes')

  

Fixed code:
n = int(input())
words =[]
words.append(input().rstrip())
 
for _ in range(1, n):
  s = input().rstrip()
  if s[0] != words[-1][-1] or s in words:
    print('No')
    break
  words.append(s)
else:
  print('Yes')
Buggy code:
# B
N = int(input())

W = []
re = 'Yes'
last = ''
for i in range(N):
    W.append(input())
    if last != '' and last != W[i][0:1]:
        re = 'No'
    elif W.count(W[i]) >= 2:
        re = 'No'
        
print(re)

Fixed code:
# B
N = int(input())

W = []
re = 'Yes'
last = ''
for i in range(N):
    W.append(input())
    if last != '' and last != W[i][0:1]:
        re = 'No'
    elif W.count(W[i]) >= 2:
        re = 'No'
    last = W[i][-1]
        
print(re)
Buggy code:
n = int(input())
l = [input() for _ in range(n)]
s = set(l)
if(len(l) != len(s)):
    print('No')
    exit()
for i in range(1,n):
    if(l[i][0] != l[i][-1]):
        print('No')
        exit()
print('Yes')

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

tmpW = input()
past = set()
flag = True
for i in range(N-1):
  W = input()
  if(tmpW[-1:] != W[0:1]):
    flag = False
  elif(W in past):
    flag = False
  tmpW = W
  
  past.add(W)

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

Fixed code:
N = int(input())

tmpW = input()
past = set()
past.add(tmpW)
flag = True
for i in range(N - 1):
    W = input()
    if(tmpW[-1:] != W[0:1]):
        flag = False
    elif(W in past):
        flag = False
    tmpW = W

    past.add(W)
    # print(past)

if(flag is True):
    print("Yes")
else:
    print("No")
Buggy code:
n = int(input())
s2=list(input())
k = 0
w = []
r = ''
for i in range(len(s2)):
    r += s2[i]
w.append(r)
for i in range(1,n):
    s=list(input())
    if s[0]!=s2[len(s2)-1]:
        k = 2
    r = ''
    for j in range(len(s)):
        r += s[j]
    #print(w,r,w.count(r))
    if w.count(r) != 0:
        k = 1
    w.append(r)
    s2 = s
if k == 1:
    print('No')
else:
    print('Yes')

Fixed code:
n = int(input())
s2=list(input())
k = 0
w = []
r = ''
for i in range(len(s2)):
    r += s2[i]
w.append(r)
for i in range(1,n):
    s=list(input())
    if s[0]!=s2[len(s2)-1]:
        k = 1
    r = ''
    for j in range(len(s)):
        r += s[j]
    #print(w,r,w.count(r))
    if w.count(r) != 0:
        k = 1
    w.append(r)
    s2 = s
if k == 1:
    print('No')
else:
    print('Yes')
Buggy code:
Row = int(input())
flag = True
List = []
for i in range (Row):
  List.append(int(input()))
s_l = set(List)
if len(List) != len(s_l):
  print("No")
for i in range(Row-1):
  n = len(List[i])-1
  if List[i][n] != List[i+1][0]:
    flag = False
if flag:
  print("Yes")
else:
  print("No")

Fixed code:
Row = int(input())
flag = True
List = []
for i in range (Row):
  List.append(input())
s_l = set(List)
if len(List) != len(s_l):
  print("No")
else:
  for i in range(Row-1):
    n = len(List[i])-1
    if List[i][n] != List[i+1][0]:
      flag = False
  if flag:
    print("Yes")
  else:
    print("No")
Buggy code:
N=int(input())
x=[input() for _ in range(N)]
flag=0

if len(x)!=len(list(set(x))):
  flag=1
  
for i in range(N):
  if x[i][-1]!=x[i][0]:
    flag=1
if flag==0:
  print("Yes")
else:
  print("No")

Fixed code:
N=int(input())
x=[input() for _ in range(N)]
flag=0

if len(x)!=len(list(set(x))):
  flag=1

for i in range(N-1):
  if x[i][-1]!=x[i+1][0]:
    flag=1
if flag==0:
  print("Yes")
else:
  print("No")
Buggy code:
n=int(input())
li=["0"]
for i in range(n):
    x=str(input())
    y=li[-1]
    if x in li or y[-1]!=x[0]:
        print("No")
        exit()
    else:
        li.append(x)
print("Yes")        
    

Fixed code:
n=int(input())
li=[str(input())]
for i in range(n-1):
    x=str(input())
    y=li[-1]
    if x in li or y[-1]!=x[0]:
        print("No")
        exit()
    else:
        li.append(x)
print("Yes")
Buggy code:
N = int(input())
a = input().strip()
ind = 0
hist = [a]
for _ in range(N-1):
    b = input().strip()
    if b in hist or a[-1]!=b[0]:
        ind = 1
        break
    hist.append(b)
    a = b
if ind==0:
    print("Yest")
else:
    print("No")

Fixed code:
N = int(input())
a = input().strip()
ind = 0
hist = [a]
for _ in range(N-1):
    b = input().strip()
    if b in hist or a[-1]!=b[0]:
        ind = 1
        break
    hist.append(b)
    a = b
if ind==0:
    print("Yes")
else:
    print("No")
Buggy code:
n = int(input())
word_list = []
ans = "Yes"
preword = input()

for i in range(n-1):
    w = input()
    if w in word_list:
        ans = "No"
    if preword[-1] != w[0]:
        ans = "No"
    word_list.append(w)
    preword = w
print(ans)

Fixed code:
n = int(input())
word_list = []
ans = "Yes"
preword = input()
word_list.append(preword)
for i in range(n-1):
    w = input()
    if w in word_list:
        ans = "No"
    if preword[-1] != w[0]:
        ans = "No"
    word_list.append(w)
    preword = w
print(ans)
Buggy code:
n = int(input())
w_li = [input() for _ in range(n)]

if len(set(w_li)) != len(w_li):
    print("No")
else:
    for i in range(n-1):
        if w_li[i][-1] != w_li[i+1][0]:
            print("No")
            break
        else:
            continue


Fixed code:
n = int(input())
w_li = [input() for _ in range(n)]

if len(set(w_li)) != len(w_li):
    print("No")
else:
    for i in range(n-1):
        if w_li[i][-1] != w_li[i+1][0]:
            print("No")
            break
        elif i == n-2:
            print("Yes")
            break
        else:
            continue
Buggy code:
import sys
N = int(input())
k = input()
a = []
for i in range(N-1):
    a.append(input())
lis = []
for words in a:
  if words in lis:
    print('No')
    sys.exit()
  elif k[-1] != words[0]:
    print('No')
    sys.exit()
  else:
    lis.append(words)
    k = words
print('Yes')

Fixed code:
import sys
N = int(input())
k = input()
a = []
for i in range(N-1):
    a.append(input())
lis = [k]
for words in a:
  if words in lis:
    print('No')
    sys.exit()
  elif k[-1] != words[0]:
    print('No')
    sys.exit()
  else:
    lis.append(words)
    k = words
print('Yes')
Buggy code:
n=int(input())
s=[input()]
count=1
for i in range(n-1):
    w=input()
    s.append(w)
    if s[i][-1]==s[i+1][0]:
        count=count+1
if count==n and len(s)==len(set(s)):
    print("Yes")
else:
    print("no")

Fixed code:
n=int(input())
s=[input()]
count=1
for i in range(n-1):
    w=input()
    s.append(w)
    if s[i][-1]==s[i+1][0]:
        count=count+1
if count==n and len(s)==len(set(s)):
    print("Yes")
else:
    print("No")
Buggy code:
N = int(input())
words = [input() for _ in range(N)]

for i, w in enumerate(words):
    if words.count(w) > 1:
        print('No')
        break
    if w[0] != words[i - 1][-1]:
        print('No')
        break
else:
    print('Yes')

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

for i, w in enumerate(words):
    if i == 0:
        continue
    if words.count(w) > 1:
        print('No')
        break
    if w[0] != words[i - 1][-1]:
        print('No')
        break
else:
    print('Yes')
Buggy code:
N = int(input())
W = [str(input()) for i in range(0, N)]

done = 0
for idx, i in enumerate(W, 1):
    if W[idx - 1][len(W[idx - 1]) - 1] != i[len(i) - 1]:
        break
    done += 1

if done == len(W) and len(set(W)) == len(W):
    print("Yes")
else:
    print("No")

Fixed code:
N = int(input())
W = [str(input()) for i in range(0, N)]

done = 0
for idx, i in enumerate(W[1:], 1):
    if W[idx - 1][len(W[idx - 1]) - 1] != i[0]:
        break
    done += 1

if done + 1 == len(W) and len(set(W)) == len(W):
    print("Yes")
else:
    print("No")
Buggy code:
n = int(input())

flag = True
chr = 'A'
table = []
for i in range(n):
    line = input()
    if chr == line[0]:
        print('No')
        flag = False
        break

    if line in table:
        print('No')
        flag = False
        break
    table.append(line)
    chr = line[-1]

if flag:
    print('Yes')


Fixed code:
n = int(input())

flag = True
chr = 'A'
table = []
for i in range(n):
    line = input()
    if not(chr == line[0] or chr == 'A'):
        print('No')
        flag = False
        break

    if line in table:
        print('No')
        flag = False
        break
    table.append(line)
    chr = line[-1]

if flag:
    print('Yes')
Buggy code:
n = int(input())
alist = [input() for i in range(n)]

for i in range(n):
  if all(alist[i][-1]==alist[i+1][0]):
    if len(set(alist))==n:
      print("Yes")
    else:
      print("No")

Fixed code:
n = int(input())
alist = [input() for i in range(n)]
 
if len(set(alist))==n:
  if all(alist[i][-1]==alist[i+1][0] for i in range(n-1)):
    print("Yes")
    exit()
print("No")
Buggy code:
words = []
for inp in range(N):
	words.append(input())

frst = words[0]
for i in range(1,len(words)):
	if words[i-1][-1] != words[i][0]:
		print("No")
		break
	else:
		flag = 0
		if words[i] in words[:i-1]:
			print("No")
			break
		else:
			flag = 1
if flag == 1:
	print("Yes")  

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

frst = words[0]
wrds = set(words)
if len(wrds) != len(words):
	print("No")
else:	
	for i in range(1,len(words)):
		flag = 1
		if words[i-1][-1] != words[i][0]:
			print("No")
			flag = 0
			break
	if flag == 1:
		print("Yes")
Buggy code:
N = int(input())
A = [[input()] for _ in range(N)]
for i in range(N):
  if b==A[i][0]:
    b= A[i][-1]
  else:
    print("No")
    exit()
A.sort()
for i in range(N-1):
  if A[i]==A[i+1]:
    print("No")
    exit()
print("Yes")

Fixed code:
N = int(input())
A = [input() for _ in range(N)]
b=A[0][0]
for i in range(N):
  if b==A[i][0]:
    b=A[i][-1]
  else:
    print("No")
    exit()
A.sort()
for i in range(N-1):
  if A[i]==A[i+1]:
    print("No")
    exit()
print("Yes")
Buggy code:
n=int(input())
w=[input() for i in range(w)]
ans="Yes"
for j in range(1,len(w)):
  if w[j-1][len(w[j-1])-1]!=w[j][0]:
    ans="No"
print(ans)

Fixed code:
n=int(input())
w=[input() for i in range(n)]
ans="Yes"
if len(set(w))!=n:
  ans="No"
for j in range(1,len(w)):
  if w[j-1][-1]!=w[j][0]:
    ans="No"
print(ans)
Buggy code:
import sys

stdin = sys.stdin

ni = lambda: int(ns())
na = lambda: list(map(int, stdin.readline().split()))
ns = lambda: stdin.readline().rstrip()  # ignore trailing spaces

n = ni()
word = input()
li = [word]
end = word[-1]
ans = 'Yes'
for i in range(n):
    word = input()
    if word[0] != end or word in li:
        ans = 'No'
        break
    end = word[-1]
    li.append(word)
print(ans)

Fixed code:
import sys

stdin = sys.stdin

ni = lambda: int(ns())
na = lambda: list(map(int, stdin.readline().split()))
ns = lambda: stdin.readline().rstrip()  # ignore trailing spaces

n = ni()
word = input()
li = [word]
end = word[-1]
ans = 'Yes'
for i in range(n-1):
    word = input()
    if word[0] != end or word in li:
        ans = 'No'
        break
    end = word[-1]
    li.append(word)
print(ans)
Buggy code:
N = int(input())
W = []
for i in range (0,N):
    W.append(input())
ans = "Yes"
d = dict()
count = 0
for j in W:
    if j in d.keys():
        ans = "No"
    else:
        d[j] = 1
    if count != 0:
        if j[0] != W[count - 1][-1]:
            ans = "No"
    else:
        count = True
print(ans)

Fixed code:
N = int(input())
W = []
for i in range (0,N):
    W.append(input())
ans = "Yes"
d = dict()
count = 0
for j in W:
    if j in d.keys():
        ans = "No"
    else:
        d[j] = 1
    if count != 0:
        if j[0] != W[count - 1][-1]:
            ans = "No"
    count += 1
print(ans)
Buggy code:
n  = int(input())
w = []

w.append(input())

ans = 'Yes'
for i in range(1,n,1):
  w.append(input())
  l = len(w[j])
  if w[i][0:1] != w[j][l-1:l]: ans = 'No'
  for j in range(i):
    if w[i] == w[j]: ans = 'No'

print(ans)

Fixed code:
n  = int(input())
w = []

w.append(input())

ans = 'Yes'
for i in range(1,n,1):
  w.append(input())
  l = len(w[i-1])
  if w[i][0:1] != w[i-1][l-1:l]:
    ans = 'No'
    break
  for j in range(i):
    if w[i] == w[j]:
      ans = 'No'
      break

print(ans)
Buggy code:
N = int(input().strip())
sirito_list = []
is_siritori = True
for _ in range(N):
  if not sirito_list:
    sirito_list.append(input().strip())
  else:
    tmp_word = input().strip()
    if tmp_word[0] != sirito_list[-1][-1] or tmp_word in sirito_list:
      print('No')
      is_siritori = False
      break
if is_siritori:
  print('Yes')

Fixed code:
N = int(input().strip())
sirito_list = []
is_siritori = True
for _ in range(N):
  if not sirito_list:
    sirito_list.append(input().strip())
  else:
    tmp_word = input().strip()
    if tmp_word[0] != sirito_list[-1][-1] or tmp_word in sirito_list:
      print('No')
      is_siritori = False
      break
    else:
      sirito_list.append(tmp_word)
if is_siritori:
  print('Yes')
Buggy code:
N=int(input())
A=[]
W=input()
A.append(W)
ans=True
for i in range(N-1):
    w=input()
    if (W[-1]!=w[0]) or (w in A):
        ans=False
    else:
        A.append(w)
else:
    print('Yes' if ans==True else 'No')

Fixed code:
N=int(input())
A=[]
W=input()
A.append(W)
ans=True
for i in range(N-1):
    w=input()
    if ((A[-1])[-1]!=w[0]) or (w in A):
        ans=False
    else:
        A.append(w)
else:
    print('Yes' if ans==True else 'No')