Problem:


Score : 500 points

Problem Statement

N players will participate in a tennis tournament. We will call them Player 1, Player 2, \ldots, Player N.

The tournament is round-robin format, and there will be N(N-1)/2 matches in total.
Is it possible to schedule these matches so that all of the following conditions are satisfied? If the answer is yes, also find the minimum number of days required.

Each player plays at most one matches in a day.

Each player i (1 \leq i \leq N) plays one match against Player A_{i, 1}, A_{i, 2}, \ldots, A_{i, N-1} in this order.

Constraints

3 \leq N \leq 1000

1 \leq A_{i, j} \leq N

A_{i, j} \neq i

A_{i, 1}, A_{i, 2}, \ldots, A_{i, N-1} are all different.

Input

Input is given from Standard Input in the following format:

N
A_{1, 1} A_{1, 2} \ldots A_{1, N-1}
A_{2, 1} A_{2, 2} \ldots A_{2, N-1}
:
A_{N, 1} A_{N, 2} \ldots A_{N, N-1}

Output

If it is possible to schedule all the matches so that all of the conditions are satisfied, print the minimum number of days required; if it is impossible, print -1.

Sample Input 1

3
2 3
1 3
1 2

Sample Output 1

3

All the conditions can be satisfied if the matches are scheduled for three days as follows:

Day 1: Player 1 vs Player 2

Day 2: Player 1 vs Player 3

Day 3: Player 2 vs Player 3

This is the minimum number of days required.

Sample Input 2

4
2 3 4
1 3 4
4 1 2
3 1 2

Sample Output 2

4

All the conditions can be satisfied if the matches are scheduled for four days as follows:

Day 1: Player 1 vs Player 2, Player 3 vs Player 4

Day 2: Player 1 vs Player 3

Day 3: Player 1 vs Player 4, Player 2 vs Player 3

Day 4: Player 2 vs Player 4

This is the minimum number of days required.

Sample Input 3

3
2 3
3 1
1 2

Sample Output 3

-1

Any scheduling of the matches violates some condition.



Sample input:
3
2 3
1 3
1 2


Sample output:
3

Submission status: Time Limit Exceeded

Solution code:
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1
  a[i]=a[i][::-1]
    
from collections import deque
q=deque()

#seen=[[False for j in range(N)] for i in range(N)]

# 選手nが試合できるならqueに入れる
def check(i):
  if len(a[i])==0:
    return False
  j=a[i][-1]
  if a[j][-1]==i:
    q.append([i,j])
  
for i in range(N):
  check(i)
  
from collections import defaultdict

day=0
while q:
  day+=1
  q=sorted(q)
  prevQ=q.copy()
  q=deque()
  matched=defaultdict(list)
  for p in prevQ:
    i=p[0]
    j=p[1]
    if i>j:
      i,j=j,i
    if matched[i]:
      continue
    a[i].pop()
    a[j].pop()
    check(i)
    check(j)
    matched[i].append(j)
    
for i in range(N):
  if len(a[i])!=0:
    print(-1)
    break
else:
  print(day)

Submission status: Time Limit Exceeded

Solution code:
import sys
from collections import deque
sys.setrecursionlimit(10**9)
INF=10**18
def input():
    return sys.stdin.readline().rstrip()

def main():
    N=int(input())
    d={}
    c=0
    edge1=[[] for _ in range(N*(N-1)//2)]
    edge2=[[] for _ in range(N*(N-1)//2)]
    for i in range(N):
        l=list(map(lambda x: int(x)-1,input().split()))
        prev=-1
        for x in l:
            if min(i,x)*10**3+max(i,x) in d:
                if prev!=-1:
                    edge1[prev].append(d[min(i,x)*10**3+max(i,x)])
                    edge2[d[min(i,x)*10**3+max(i,x)]].append(prev)
            else:
                d[min(i,x)*10**3+max(i,x)]=c
                if prev!=-1:
                    edge1[prev].append(c)
                    edge2[c].append(prev)
                c+=1
            prev=d[min(i,x)*10**3+max(i,x)]
    queue=deque()
    days=[-1]*(N*(N-1)//2)
    for i,l in enumerate(edge2):
        if not l:
            queue.append(i)
            days[i]=1
    if queue:
        for _ in range(10**7):
            v=queue.popleft()
            for x in edge1[v]:
                if days[x]<days[v]+1:
                    days[x]=days[v]+1
                    queue.append(x)
            if not queue:
                print(max(days))
                exit()
    print(-1)
        

    

        
if __name__ == '__main__':
    main()

Submission status: Time Limit Exceeded

Solution code:
import sys
sys.setrecursionlimit(10**9)
INF=10**18
def input():
    return sys.stdin.readline().rstrip()

def main():
    N=int(input())
    d={}
    c=0
    edge1=[[] for _ in range(N*(N-1)//2)]
    edge2=[[] for _ in range(N*(N-1)//2)]
    for i in range(N):
        l=list(map(lambda x: int(x)-1,input().split()))
        prev=-1
        for x in l:
            if min(i,x)*10**3+max(i,x) in d:
                if prev!=-1:
                    edge1[prev].append(d[min(i,x)*10**3+max(i,x)])
                    edge2[d[min(i,x)*10**3+max(i,x)]].append(prev)
            else:
                d[min(i,x)*10**3+max(i,x)]=c
                if prev!=-1:
                    edge1[prev].append(c)
                    edge2[c].append(prev)
                c+=1
            prev=d[min(i,x)*10**3+max(i,x)]
    stack=[]
    days=[-1]*(N*(N-1)//2)
    for i,l in enumerate(edge2):
        if not l:
            stack.append(i)
            days[i]=1
    if stack:
        for _ in range(2*10**7):
            v=stack.pop()
            for x in edge1[v]:
                if days[x]<days[v]+1:
                    days[x]=days[v]+1
                    stack.append(x)
            if not stack:
                print(max(days))
                exit()
    print(-1)
        

    

        
if __name__ == '__main__':
    main()

Submission status: Time Limit Exceeded

Solution code:
import sys
sys.setrecursionlimit(10**9)
INF=10**18
def input():
    return sys.stdin.readline().rstrip()

def main():
    N=int(input())
    d={}
    c=0
    edge1=[[] for _ in range(N*(N-1)//2)]
    edge2=[[] for _ in range(N*(N-1)//2)]
    for i in range(N):
        l=list(map(lambda x: int(x)-1,input().split()))
        prev=-1
        for x in l:
            if min(i,x)*10**3+max(i,x) in d:
                if prev!=-1:
                    edge1[prev].append(d[min(i,x)*10**3+max(i,x)])
                    edge2[d[min(i,x)*10**3+max(i,x)]].append(prev)
            else:
                d[min(i,x)*10**3+max(i,x)]=c
                if prev!=-1:
                    edge1[prev].append(c)
                    edge2[c].append(prev)
                c+=1
            prev=d[min(i,x)*10**3+max(i,x)]
    stack=[]
    days=[-1]*(N*(N-1)//2)
    for i,l in enumerate(edge2):
        if not l:
            stack.append(i)
            days[i]=1
    if stack:
        for _ in range(3*10**7):
            v=stack.pop()
            for x in edge1[v]:
                if days[x]<days[v]+1:
                    days[x]=days[v]+1
                    stack.append(x)
            if not stack:
                print(max(days))
                exit()
    print(-1)
        

    

        
if __name__ == '__main__':
    main()

Submission status: Time Limit Exceeded

Solution code:
import sys
sys.setrecursionlimit(10**9)
INF=10**18
def input():
    return sys.stdin.readline().rstrip()

def main():
    N=int(input())
    d={}
    c=0
    edge1=[[] for _ in range(N*(N-1)//2)]
    edge2=[[] for _ in range(N*(N-1)//2)]
    for i in range(N):
        l=list(map(lambda x: int(x)-1,input().split()))
        prev=-1
        for x in l:
            if min(i,x)*10**3+max(i,x) in d:
                if prev!=-1:
                    edge1[prev].append(d[min(i,x)*10**3+max(i,x)])
                    edge2[d[min(i,x)*10**3+max(i,x)]].append(prev)
            else:
                d[min(i,x)*10**3+max(i,x)]=c
                if prev!=-1:
                    edge1[prev].append(c)
                    edge2[c].append(prev)
                c+=1
            prev=d[min(i,x)*10**3+max(i,x)]
    stack=[]
    days=[-1]*(N*(N-1)//2)
    for i,l in enumerate(edge2):
        if not l:
            stack.append(i)
            days[i]=1
    if stack:
        for _ in range(5*10**7):
            v=stack.pop()
            for x in edge1[v]:
                if days[x]<days[v]+1:
                    days[x]=days[v]+1
                    stack.append(x)
            if not stack:
                print(max(days))
                exit()
    print(-1)
        

    

        
if __name__ == '__main__':
    main()

Submission status: Time Limit Exceeded

Solution code:
import sys
sys.setrecursionlimit(10**9)
INF=10**18
def input():
    return sys.stdin.readline().rstrip()

def main():
    N=int(input())
    d={}
    c=0
    edge1=[[] for _ in range(N*(N-1)//2)]
    edge2=[[] for _ in range(N*(N-1)//2)]
    for i in range(N):
        l=list(map(lambda x: int(x)-1,input().split()))
        prev=-1
        for x in l:
            if min(i,x)*10**3+max(i,x) in d:
                if prev!=-1:
                    edge1[prev].append(d[min(i,x)*10**3+max(i,x)])
                    edge2[d[min(i,x)*10**3+max(i,x)]].append(prev)
            else:
                d[min(i,x)*10**3+max(i,x)]=c
                if prev!=-1:
                    edge1[prev].append(c)
                    edge2[c].append(prev)
                c+=1
            prev=d[min(i,x)*10**3+max(i,x)]
    stack=[]
    d=[-1]*(N*(N-1)//2)
    for i,l in enumerate(edge2):
        if not l:
            stack.append(i)
            d[i]=1
    while stack:
        v=stack.pop()
        for x in edge1[v]:
            d[x]=max(d[x],d[v]+1)
            stack.append(x)
    print(max(d))
        

    

        
if __name__ == '__main__':
    main()

Submission status: Time Limit Exceeded

Solution code:
import sys
input = sys.stdin.readline

from collections import deque

def main():

    n = int(input())
    
    a = [[int(i) for i in input().split()] for j in range(n)]
    
    check = [0]*n
    used = [0]*n
    
    d = deque()
    
    for i in range(n):
        if used[i] == 1:
            continue
        ai = a[i][0]-1
        if a[ai][0] == i+1:
            d.append([i+1,ai+1])
            used[i] = 1
            used[ai] = 1
            check[i] = 1
            check[ai] = 1
            
    ans = 0
    
    if len(d) == 0:
        print(-1)
        exit()
    
    #print(d)
    
    while len(d) > 0:
        used = [0]*n
        ans += 1
        num = len(d)
        for i in range(num):
            tmp = d.popleft()
            for j in range(2):
                mys = tmp[j]-1
                if check[mys] != n-1 and used[mys] == 0:
                    psn = a[mys][check[mys]]-1
                    if check[psn] != n-1 and used[psn] == 0:
                    #print(tmp,psn,a[psn][check[psn]])
                    #print(i,j,tmp,psn,check[mys],check[psn])
        
                        if a[psn][check[psn]] == mys+1:
                            d.append([psn+1,mys+1])
                            used[mys] = 1
                            used[psn] = 1
                            check[mys] += 1
                            check[psn] += 1
        #print(d)
        
    for i in range(n):
        if check[i] != n-1:
            print(-1)
            exit()
    
    print(ans)

if __name__ == '__main__':
    main()

Submission status: Time Limit Exceeded

Solution code:
import sys
input = sys.stdin.readline

from collections import deque

def main():

    n = int(input())
    
    a = [[int(i) for i in input().split()] for j in range(n)]
    
    check = [0]*n
    used = [False]*n
    
    d = deque()
    
    for i in range(n):
        if used[i] == True:
            continue
        ai = a[i][0]-1
        if a[ai][0] == i+1:
            d.append([i+1,ai+1])
            used[i] = True
            used[ai] = True
            check[i] = 1
            check[ai] = 1
            
    ans = 0
    
    if len(d) == 0:
        print(-1)
        exit()
    
    #print(d)
    
    while len(d) > 0:
        used = [False]*n
        ans += 1
        num = len(d)
        for i in range(num):
            tmp = d.popleft()
            for j in range(2):
                mys = tmp[j]-1
                if check[mys] != n-1 and used[mys] == False:
                    psn = a[mys][check[mys]]-1
                    if check[psn] != n-1 and used[psn] == False:
                    #print(tmp,psn,a[psn][check[psn]])
                    #print(i,j,tmp,psn,check[mys],check[psn])
        
                        if a[psn][check[psn]] == mys+1:
                            d.append([psn+1,mys+1])
                            used[mys] = True
                            used[psn] = True
                            check[mys] += 1
                            check[psn] += 1
        #print(d)
        
    for i in range(n):
        if check[i] != n-1:
            print(-1)
            exit()
    
    print(ans)

if __name__ == '__main__':
    main()

Submission status: Time Limit Exceeded

Solution code:
import sys
input = sys.stdin.readline

from collections import deque

def main():

    n = int(input())
    
    a = [[int(i) for i in input().split()] for j in range(n)]
    
    check = [0]*n
    used = [False]*n
    
    d = deque()
    
    for i in range(n):
        if used[i] == True:
            continue
        ai = a[i][0]-1
        if a[ai][0] == i+1:
            d.append([i+1,ai+1])
            used[i] = True
            used[ai] = True
            check[i] = 1
            check[ai] = 1
            
    ans = 0
    
    if len(d) == 0:
        print(-1)
        exit()
    
    #print(d)
    
    while len(d) > 0:
        used = [False]*n
        ans += 1
        num = len(d)
        for i in range(num):
            tmp = d.popleft()
            
            j = 0
            mys = tmp[j]-1
            if check[mys] != n-1 and used[mys] == False:
                psn = a[mys][check[mys]]-1
                if check[psn] != n-1 and used[psn] == False:
                #print(tmp,psn,a[psn][check[psn]])
                #print(i,j,tmp,psn,check[mys],check[psn])
    
                    if a[psn][check[psn]] == mys+1:
                        d.append([psn+1,mys+1])
                        used[mys] = True
                        used[psn] = True
                        check[mys] += 1
                        check[psn] += 1
                        
            j = 1
            mys = tmp[j]-1
            if check[mys] != n-1 and used[mys] == False:
                psn = a[mys][check[mys]]-1
                if check[psn] != n-1 and used[psn] == False:
                #print(tmp,psn,a[psn][check[psn]])
                #print(i,j,tmp,psn,check[mys],check[psn])
    
                    if a[psn][check[psn]] == mys+1:
                        d.append([psn+1,mys+1])
                        used[mys] = True
                        used[psn] = True
                        check[mys] += 1
                        check[psn] += 1
        #print(d)
        
    for i in range(n):
        if check[i] != n-1:
            print(-1)
            exit()
    
    print(ans)

if __name__ == '__main__':
    main()

Submission status: Time Limit Exceeded

Solution code:
import sys
input = sys.stdin.readline

from collections import deque

def main():

    n = int(input())
    
    a = [[int(i) for i in input().split()] for j in range(n)]
    
    check = [0]*n
    used = [False]*n
    
    d = deque()
    
    for i in reversed(range(n)):
        if used[i] == True:
            continue
        ai = a[i][0]-1
        if a[ai][0] == i+1:
            d.append([i+1,ai+1])
            used[i] = True
            used[ai] = True
            check[i] = 1
            check[ai] = 1
            
    ans = 0
    
    if len(d) == 0:
        print(-1)
        exit()
    
    #print(d)
    
    while len(d) > 0:
        used = [False]*n
        ans += 1
        num = len(d)
        for i in range(num):
            tmp = d.popleft()
            for j in range(2):
                mys = tmp[j]-1
                if check[mys] == n-1 or used[mys] == True:
                    continue
                psn = a[mys][check[mys]]-1
                
                if check[psn] == n-1 or used[psn] == True:
                    continue
                #print(tmp,psn,a[psn][check[psn]])
                #print(i,j,tmp,psn,check[mys],check[psn])
    
                if a[psn][check[psn]] == mys+1:
                    d.append([psn+1,mys+1])
                    used[mys] = True
                    used[psn] = True
                    check[mys] += 1
                    check[psn] += 1
        #print(d)
        
    for i in range(n):
        if check[i] != n-1:
            print(-1)
            exit()
    
    print(ans)

if __name__ == '__main__':
    main()

Submission status: Time Limit Exceeded

Solution code:
import sys
input = sys.stdin.readline

from collections import deque

def main():

    n = int(input())
    
    a = [[int(i) for i in input().split()] for j in range(n)]
    
    check = [0]*n
    used = [False]*n
    
    d = deque()
    
    for i in reversed(range(n)):
        if used[i] == True:
            continue
        ai = a[i][0]-1
        if a[ai][0] == i+1:
            d.appendleft([i+1,ai+1])
            used[i] = True
            used[ai] = True
            check[i] = 1
            check[ai] = 1
            
    ans = 0
    
    if len(d) == 0:
        print(-1)
        exit()
    
    #print(d)
    
    while len(d) > 0:
        used = [False]*n
        ans += 1
        num = len(d)
        for i in range(num):
            tmp = d.popleft()
            for j in range(2):
                mys = tmp[j]-1
                if check[mys] == n-1 or used[mys] == True:
                    continue
                psn = a[mys][check[mys]]-1
                
                if check[psn] == n-1 or used[psn] == True:
                    continue
                #print(tmp,psn,a[psn][check[psn]])
                #print(i,j,tmp,psn,check[mys],check[psn])
    
                if a[psn][check[psn]] == mys+1:
                    d.append([psn+1,mys+1])
                    used[mys] = True
                    used[psn] = True
                    check[mys] += 1
                    check[psn] += 1
        #print(d)
        
    for i in range(n):
        if check[i] != n-1:
            print(-1)
            exit()
    
    print(ans)

if __name__ == '__main__':
    main()

Submission status: Time Limit Exceeded

Solution code:
import sys
input = sys.stdin.readline

from collections import deque

def main():

    n = int(input())
    
    a = [[int(i) for i in input().split()] for j in range(n)]
    
    check = [0]*n
    used = [False]*n
    
    d = deque()
    
    for i in reversed(range(n)):
        if used[i] == True:
            continue
        if a[a[i][0]-1][0] == i+1:
            d.appendleft([i+1,a[i][0]])
            used[i] = True
            used[a[i][0]-1] = True
            check[i] = 1
            check[a[i][0]-1] = 1
            
    ans = 0
    
    if len(d) == 0:
        print(-1)
        exit()
    
    #print(d)
    
    while len(d) > 0:
        used = [False]*n
        ans += 1
        num = len(d)
        for i in range(num):
            tmp = d.popleft()
            for j in range(2):
                mys = tmp[j]-1
                if check[mys] == n-1 or used[mys] == True:
                    continue
                psn = a[mys][check[mys]]-1
                
                if check[psn] == n-1 or used[psn] == True:
                    continue
                #print(tmp,psn,a[psn][check[psn]])
                #print(i,j,tmp,psn,check[mys],check[psn])
    
                if a[psn][check[psn]] == mys+1:
                    d.append([psn+1,mys+1])
                    used[mys] = True
                    used[psn] = True
                    check[mys] += 1
                    check[psn] += 1
        #print(d)
        
    for i in range(n):
        if check[i] != n-1:
            print(-1)
            exit()
    
    print(ans)

if __name__ == '__main__':
    main()

Submission status: Time Limit Exceeded

Solution code:
import sys
input = sys.stdin.readline

from collections import deque

def main():

    n = int(input())
    
    a = [[int(i) for i in input().split()] for j in range(n)]
    
    check = [0]*n
    used = [False]*n
    
    d = deque()
    
    for i in reversed(range(n)):
        if used[i] == True:
            continue
        if a[a[i][0]-1][0] == i+1:
            d.appendleft([i+1,a[i][0]])
            used[i] = True
            used[a[i][0]-1] = True
            check[i] = 1
            check[a[i][0]-1] = 1
            
    ans = 0
    
    if len(d) == 0:
        print(-1)
        exit()
    
    #print(d)
    
    while len(d) > 0:
        used = [False]*n
        ans += 1
        num = len(d)
        for i in range(num):
            tmp = d.popleft()
            for j in range(2):
                mys = tmp[j]-1
                if check[mys] == n-1:
                    continue
                if used[mys] == True:
                    continue
                psn = a[mys][check[mys]]-1
                
                if check[psn] == n-1:
                    continue
                #print(tmp,psn,a[psn][check[psn]])
                #print(i,j,tmp,psn,check[mys],check[psn])
                if used[psn] == True:
                    continue
    
                if a[psn][check[psn]] == mys+1:
                    d.append([psn+1,mys+1])
                    used[mys] = True
                    used[psn] = True
                    check[mys] += 1
                    check[psn] += 1
        #print(d)
        
    for i in range(n):
        if check[i] != n-1:
            print(-1)
            exit()
    
    print(ans)

if __name__ == '__main__':
    main()

Submission status: Time Limit Exceeded

Solution code:
import sys
input = sys.stdin.readline

from collections import deque

def main():

    n = int(input())
    
    a = [[int(i) for i in input().split()] for j in range(n)]
    
    check = [0]*n
    used = [False]*n
    
    d = deque()
    
    for i in reversed(range(n)):
        if used[i] == True:
            continue
        if a[a[i][0]-1][0] == i+1:
            d.appendleft([i+1,a[i][0]])
            used[i] = True
            used[a[i][0]-1] = True
            check[i] = 1
            check[a[i][0]-1] = 1
            
    ans = 0
    
    if len(d) == 0:
        print(-1)
        exit()
    
    #print(d)
    
    while len(d) > 0:
        used = [False]*n
        ans += 1
        num = len(d)
        for i in range(num):
            tmp = d.popleft()
            for j in range(2):
                mys = tmp[j]-1
                if check[mys] == n-1:
                    continue
                psn = a[mys][check[mys]]-1
                
                if check[mys] == n-1 or check[psn] == n-1:
                    continue
                #print(tmp,psn,a[psn][check[psn]])
                #print(i,j,tmp,psn,check[mys],check[psn])
                if used[mys] == True or used[psn] == True:
                    continue
    
                if a[psn][check[psn]] == mys+1:
                    d.append([psn+1,mys+1])
                    used[mys] = True
                    used[psn] = True
                    check[mys] += 1
                    check[psn] += 1
        #print(d)
        
    for i in range(n):
        if check[i] != n-1:
            print(-1)
            exit()
    
    print(ans)

if __name__ == '__main__':
    main()

Submission status: Time Limit Exceeded

Solution code:
import sys
input = sys.stdin.readline
import time

from collections import deque

import queue

def main():
    t1 = time.time()

    n = int(input())
    
    a = [[int(i) for i in input().split()] for j in range(n)]
    
    check = [0]*n
    used = [False]*n
    
    d = queue.Queue()
    
    #d = deque()
    
    for i in reversed(range(n)):
        if used[i] == True:
            continue
        if a[a[i][0]-1][0] == i+1:
            d.put([i+1,a[i][0]])
            used[i] = True
            used[a[i][0]-1] = True
            check[i] = 1
            check[a[i][0]-1] = 1
            
    ans = 0
    
    if d.empty():
        print(-1)
        exit()
    
    #print(d)
    
    while not d.empty():
        used = [False]*n
        ans += 1
        num = d.qsize()
        for i in range(num):
            tmp = d.get()
            for j in range(2):
                if check[tmp[j]-1] == n-1:
                    continue
                psn = a[tmp[j]-1][check[tmp[j]-1]]-1
                mys = tmp[j]-1
                
                if check[mys] == n-1 or check[psn] == n-1:
                    continue
                #print(tmp,psn,a[psn][check[psn]])
                #print(i,j,tmp,psn,check[mys],check[psn])
                if used[mys] == True or used[psn] == True:
                    continue
    
                if a[psn][check[psn]] == mys+1:
                    d.put([psn+1,mys+1])
                    used[mys] = True
                    used[psn] = True
                    check[mys] += 1
                    check[psn] += 1
        #print(d)
        
    for i in range(n):
        if check[i] != n-1:
            print(-1)
            exit()
    
    print(ans)

if __name__ == '__main__':
    main()

Submission status: Time Limit Exceeded

Solution code:
import sys
input = sys.stdin.readline

from collections import deque

def main():

    n = int(input())
    
    a = [[int(i) for i in input().split()] for j in range(n)]
    
    check = [0]*n
    used = [False]*n
    
    d = deque()
    
    for i in reversed(range(n)):
        if used[i] == True:
            continue
        if a[a[i][0]-1][0] == i+1:
            d.appendleft([i+1,a[i][0]])
            used[i] = True
            used[a[i][0]-1] = True
            check[i] = 1
            check[a[i][0]-1] = 1
            
    ans = 0
    
    if len(d) == 0:
        print(-1)
        exit()
    
    #print(d)
    
    while len(d) > 0:
        used = [False]*n
        ans += 1
        num = len(d)
        for i in range(num):
            tmp = d.popleft()
            for j in range(2):
                if check[tmp[j]-1] == n-1:
                    continue
                psn = a[tmp[j]-1][check[tmp[j]-1]]-1
                mys = tmp[j]-1
                
                if check[mys] == n-1 or check[psn] == n-1:
                    continue
                #print(tmp,psn,a[psn][check[psn]])
                #print(i,j,tmp,psn,check[mys],check[psn])
                if used[mys] == True or used[psn] == True:
                    continue
    
                if a[psn][check[psn]] == mys+1:
                    d.append([psn+1,mys+1])
                    used[mys] = True
                    used[psn] = True
                    check[mys] += 1
                    check[psn] += 1
        #print(d)
        
    for i in range(n):
        if check[i] != n-1:
            print(-1)
            exit()
    
    print(ans)

if __name__ == '__main__':
    main()

Submission status: Time Limit Exceeded

Solution code:
import sys
input = sys.stdin.readline

from collections import deque

n = int(input())

a = [[int(i) for i in input().split()] for j in range(n)]

check = [0]*n
used = [False]*n

d = deque()

for i in reversed(range(n)):
    if used[i] == True:
        continue
    if a[a[i][0]-1][0] == i+1:
        d.appendleft([i+1,a[i][0]])
        used[i] = True
        used[a[i][0]-1] = True
        check[i] = 1
        check[a[i][0]-1] = 1
        
ans = 0

if len(d) == 0:
    print(-1)
    exit()

#print(d)

while len(d) > 0:
    used = [False]*n
    ans += 1
    num = len(d)
    for i in range(num):
        tmp = d.popleft()
        for j in range(2):
            if check[tmp[j]-1] == n-1:
                continue
            psn = a[tmp[j]-1][check[tmp[j]-1]]-1
            mys = tmp[j]-1
            
            if check[mys] == n-1 or check[psn] == n-1:
                continue
            #print(tmp,psn,a[psn][check[psn]])
            #print(i,j,tmp,psn,check[mys],check[psn])
            if used[mys] == True or used[psn] == True:
                continue

            if a[psn][check[psn]] == mys+1:
                d.append([psn+1,mys+1])
                used[mys] = True
                used[psn] = True
                check[mys] += 1
                check[psn] += 1
    #print(d)
    
for i in range(n):
    if check[i] != n-1:
        print(-1)
        exit()

print(ans)

Submission status: Time Limit Exceeded

Solution code:
from collections import deque

n = int(input())

a = [[int(i) for i in input().split()] for j in range(n)]

check = [0]*n
used = [False]*n

d = deque()

for i in reversed(range(n)):
    if used[i] == True:
        continue
    if a[a[i][0]-1][0] == i+1:
        d.appendleft([i+1,a[i][0]])
        used[i] = True
        used[a[i][0]-1] = True
        check[i] = 1
        check[a[i][0]-1] = 1
        
ans = 0

if len(d) == 0:
    print(-1)
    exit()

#print(d)

while len(d) > 0:
    used = [False]*n
    ans += 1
    num = len(d)
    for i in range(num):
        tmp = d.popleft()
        for j in range(2):
            if check[tmp[j]-1] == n-1:
                continue
            psn = a[tmp[j]-1][check[tmp[j]-1]]-1
            mys = tmp[j]-1
            
            if check[mys] == n-1 or check[psn] == n-1:
                continue
            #print(tmp,psn,a[psn][check[psn]])
            #print(i,j,tmp,psn,check[mys],check[psn])
            if used[mys] == True or used[psn] == True:
                continue

            if a[psn][check[psn]] == mys+1:
                d.append([psn+1,mys+1])
                used[mys] = True
                used[psn] = True
                check[mys] += 1
                check[psn] += 1
    #print(d)

for i in range(n):
    if check[i] != n-1:
        print(-1)
        exit()

print(ans)

Submission status: Time Limit Exceeded

Solution code:
from collections import deque

n = int(input())

a = [[int(i) for i in input().split()] for j in range(n)]

check = [0]*n
used = [False]*n

d = deque()

for i in reversed(range(n)):
    if used[i] == True:
        continue
    if a[a[i][0]-1][0] == i+1:
        d.appendleft([i+1,a[i][0]])
        used[i] = True
        used[a[i][0]-1] = True
        check[i] = 1
        check[a[i][0]-1] = 1
        
ans = 0

if len(d) == 0:
    print(-1)
    exit()

#print(d)

while len(d) > 0:
    used = [False]*n
    ans += 1
    num = len(d)
    for i in range(num):
        tmp = d.popleft()
        for j in range(2):
            if check[tmp[j]-1] == n-1:
                continue
            psn = a[tmp[j]-1][check[tmp[j]-1]]-1
            mys = tmp[j]-1
            
            if check[mys] == n-1 or check[psn] == n:
                continue
            #print(tmp,psn,a[psn][check[psn]])
            #print(i,j,tmp,psn,check[mys],check[psn])
            if used[mys] == True or used[psn] == True:
                continue

            if a[psn][check[psn]] == mys+1:
                d.append([psn+1,mys+1])
                used[mys] = True
                used[psn] = True
                check[mys] += 1
                check[psn] += 1
    #print(d)

for i in range(n):
    if check[i] != n-1:
        print(-1)
        exit()

print(ans)