Problem p02925 (python)

Fixed submission:
# YouTube1

def main():
    n = int(input())
    a = [list(map(lambda x: int(x) - 1, input().split()))[::-1] for _ in range(n)]
    #    print(a)
    gam = []  # １日のgames
    # 初期化
    for i in range(n):
        ii = a[i][-1]
        if ii < i: continue
        if a[ii][-1] == i:
            gam.append([i, ii])
    days = 0
    fin = [False] * n
    fin_cnt = 0
    #    print(gam)
    while 1:
        days += 1
        pla = []  # 今日試合があったplayers
        for i, ii in gam:
            a[i].pop()
            a[ii].pop()
            pla.append(i)
            pla.append(ii)
        gam = []
        dec = set()
        for i in pla:
            if fin[i]: continue
            if not a[i]:
                fin[i] = True
                fin_cnt += 1
                if fin_cnt == n:
                    print(days)
                    exit()
                continue
            if i in dec: continue
            ii = a[i][-1]
            if a[ii][-1] == i:
                gam.append([i, ii])
                dec.add(ii)
        if not gam:
            print(-1)
            exit()

main()

Buggy submission (verdict: Runtime Error):
# YouTube2
from collections import defaultdict
import sys
sys.setrecursionlimit(10 ** 6)
input=sys.stdin.readline

def main():
    def dfs(u):
        if dis[u] > 0:
            return dis[u]
        if dis[u] == 0:
            return -1
        dis[u] = 0
        res = 1
        for v in to[u]:
            tmp = dfs(v) + 1
            if tmp == 0: return -1
            res = max(res, tmp)
        dis[u] = res
        return res

    to = defaultdict(list)
    n = int(input()[:-1])
    a = [list(map(lambda x: int(x) - 1, input().split())) for _ in range(n)]
    all_game = n * (n - 1) // 2
    dis = [-1] * all_game
    game = [[0] * n for _ in range(n)]
    u = 0
    for i in range(n - 1):
        for j in range(i + 1, n):
            game[i][j] = game[j][i] = u
            u += 1

    for i in range(n):
        ai=a[i]
        gi=game[i]
        j = ai[0]
        pre = gi[j]
        for gi in range(1, n - 1):
            j = ai[gi]
            to[pre].append(gi[j])
            pre = gi[j]
#    print(to)

    ans=0
    for i in range(all_game):
        tmp=dfs(i)
        if tmp == -1:
            print(-1)
            exit()
        if tmp>ans:
            ans=tmp
#    print(dis)
    print(ans)

main()

Buggy submission (verdict: Runtime Error):
# YouTube2
from collections import defaultdict

def main():
    def dfs(u):
        if dis[u] > 0:
            return dis[u]
        if dis[u] == 0:
            return -1
        dis[u] = 0
        res = 1
        for v in to[u]:
            tmp = dfs(v) + 1
            if tmp == 0: return -1
            res = max(res, tmp)
        dis[u] = res
        return res

    to = defaultdict(list)
    n = int(input())
    a = [list(map(lambda x: int(x) - 1, input().split())) for _ in range(n)]
    all_game = n * (n - 1) // 2
    dis = [-1] * all_game
    game = [[0] * n for _ in range(n)]
    u = 0
    for i in range(n - 1):
        for j in range(i + 1, n):
            game[i][j] = game[j][i] = u
            u += 1

    for i in range(n):
        j = a[i][0]
        pre = game[i][j]
        for gi in range(1, n - 1):
            j = a[i][gi]
            to[pre].append(game[i][j])
            pre = game[i][j]
#    print(to)

    for i in range(all_game):
        if dfs(i) == -1:
            print(-1)
            exit()
#    print(dis)
    print(max(dis))

main()