Problem: 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.

Submission attempts (in order):
import sys
input = sys.stdin.readline
n = int(input())
a = [list(map(int, input().split()))]
ans = 0
flag = True
while True:
    tmp = 0
    for j in range(n):
        if not a[j]:
            tmp += 1
            continue
        c = a[j][0]
        if c == "-":
            continue
        if j + 1 == a[c-1][0]:
            a[j][0] = "-"
            a[c-1][0] = "-"
    if tmp == n:
        print(ans)
        break
    for j in range(n):
        if a[j]:
            if a[j][0] == "-":
                a[j] = a[j][1:]
                flag = False
    if flag:
        print(-1)
        break
    else:
        ans += 1


import sys
input = sys.stdin.readline
n = int(input())
a = [list(map(int, input().split())) for _ in range(n)]
ans = 0
flag = True
r = set(list(range(n)))
while True:
    ne = set()
    if not r:
        print(ans)
        break
    for j in r:
        if not a[j]:
            continue
        c = a[j][0]
        if c == "-":
            continue
        if j + 1 == a[c-1][0]:
            a[j][0] = "-"
            a[c-1][0] = "-"
            ne.add(j)
            ne.add(c-1)
    for j in n:
        if a[j]:
            if a[j][0] == "-":
                a[j] = a[j][1:]
                flag = False
                if not a[j]:
                    ne.remove(j)
    if flag:
        print(-1)
        break
    else:
        r = ne
        ans += 1


import sys
input = sys.stdin.readline
n = int(input())
a = [list(map(int, input().split())) for _ in range(n)]
ans = 0
r = set(list(range(n)))
N = n*(n-1) // 2 + 1
for _ in range(N):
    if not r:
        print(_)
        break
    ne = set()
    flag = True
    for j in r:
        if not a[j]:
            continue
        c = a[j][0]
        if c == "-":
            continue
        if j + 1 == a[c-1][0]:
            a[j][0] = "-"
            a[c-1][0] = "-"
            ne.add(j)
            ne.add(c-1)
    for j in list(ne):
        if a[j]:
            if a[j][0] == "-":
                a[j] = a[j].pop(0)
                flag = False
                if not a[j]:
                    ne.remove(j)
    if flag:
        print(-1)
        break
    else:
        r = ne


import sys
input = sys.stdin.readline
n = int(input())
a = [list(map(int, input().split())) for _ in range(n)]
ans = 0
r = set(list(range(n)))
N = n*(n-1) // 2 + 1
for _ in range(N):
    if not r:
        print(_)
        break
    ne = set()
    flag = True
    for j in r:
        if not a[j]:
            continue
        c = a[j][0]
        if c == "-":
            continue
        if j + 1 == a[c-1][0]:
            a[j][0] = "-"
            a[c-1][0] = "-"
            ne.add(j)
            ne.add(c-1)
    for j in list(ne):
        if a[j]:
            if a[j][0] == "-":
                a[j].pop(0)
                flag = False
                if not a[j]:
                    ne.remove(j)
    if flag:
        print(-1)
        break
    else:
        r = ne


Verdicts: Runtime Error

Runtime Error

Wrong Answer

Accepted