Buggy python submission (verdict: Time Limit Exceeded):
import sys
from collections import deque
input = sys.stdin.readline
def combination_to_index(a,b,n):
    if(b<a):
        a,b = b,a
    return (2*n-a)*(a-1)//2+b-a

def main():
    N = int(input())
    M = N*(N-1)//2
    gp = [[] for _ in range(M+1)]
    cnts = [0]*(M+1)
    for a in range(1,N+1):
        A = [int(x) for x in input().split()]
        for ind,b in enumerate(A[:-1]):
            fr = combination_to_index(a,b,N)
            to = combination_to_index(a,A[ind+1],N)
            gp[fr].append(to)
            cnts[to] += 1

    for ind,i in enumerate(cnts):
        if(i==0 and ind!=0):
            gp[0].append(ind)
            cnts[ind]+=1

    ans = 0
    cnt = 0
    stk = deque()
    stk.append((0,0))
    while stk:
        n,ans = stk.popleft()
        for x in gp[n]:
            cnts[x]-=1
            if(cnts[x]==0):
                stk.append((x,ans+1))
                cnt += 1
    if(cnt!=M):
        print(-1)
    else:
        print(ans)

if __name__ == '__main__':
    main()


Fixed submission:
import sys
from collections import deque
input = sys.stdin.readline
def combination_to_index(a,b,n):
    if(b<a):
        a,b = b,a
    return (2*n-a)*(a-1)//2+b-a

def main():
    N = int(input())
    M = N*(N-1)//2
    gp = [[] for _ in range(M+1)]
    cnts = [0]*(M+1)
    for a in range(1,N+1):
        A = [int(x) for x in input().split()]
        for ind,b in enumerate(A[:-1]):
            fr = combination_to_index(a,b,N)
            to = combination_to_index(a,A[ind+1],N)
            gp[fr].append(to)
            cnts[to] += 1

    for ind,i in enumerate(cnts):
        if(i==0 and ind!=0):
            gp[0].append(ind)
            cnts[ind]+=1

    ans = 0
    cnt = 0
    stk = deque()
    stk.append((0,0))
    while stk:
        n,ans = stk.popleft()
        for x in gp[n]:
            cnts[x]-=1
            if(cnts[x]==0):
                stk.append((x,ans+1))
                cnt += 1
    if(cnt!=M):
        print(-1)
    else:
        print(ans)

if __name__ == '__main__':
    main()

Buggy python submission (verdict: Time Limit Exceeded):
import sys
sys.setrecursionlimit(1000000)
input = sys.stdin.readline

def combination_to_index(a,b,n):
    if(b<a):
        c = a
        a = b
        b = c
    return (2*n-a)*(a-1)//2+b-a

def main():
    N = int(input())
    M = N*(N-1)//2
    gp = [[] for _ in range(M+1)]
    cnts = [0]*(M+1)
    for a in range(1,N+1):
        A = [int(x) for x in input().split()]
        for ind,b in enumerate(A[:-1]):
            fr = combination_to_index(a,b,N)
            to = combination_to_index(a,A[ind+1],N)
            gp[fr].append(to)
            cnts [to] += 1

    for ind,i in enumerate(cnts):
        if(i==0 and ind!=0):
            gp[0].append(ind)

    max_d = 0
    stk = []
    stk.append((0,set(),0))
    while stk:
        nxt = []
        n,seen,d = stk.pop()
        res = -1
        if(n in seen):
            continue
        max_d = max(max_d,d)
        for x in gp[n]:
            nxt.append((x,seen.union(set([n])),d+1))
        stk = nxt+stk

    if(max_d==0):
        print(-1)
    else:
        print(max_d)

if __name__ == '__main__':
    main()


Fixed submission:
import sys
from collections import deque
input = sys.stdin.readline
def combination_to_index(a,b,n):
    if(b<a):
        a,b = b,a
    return (2*n-a)*(a-1)//2+b-a

def main():
    N = int(input())
    M = N*(N-1)//2
    gp = [[] for _ in range(M+1)]
    cnts = [0]*(M+1)
    for a in range(1,N+1):
        A = [int(x) for x in input().split()]
        for ind,b in enumerate(A[:-1]):
            fr = combination_to_index(a,b,N)
            to = combination_to_index(a,A[ind+1],N)
            gp[fr].append(to)
            cnts[to] += 1

    for ind,i in enumerate(cnts):
        if(i==0 and ind!=0):
            gp[0].append(ind)
            cnts[ind]+=1

    ans = 0
    cnt = 0
    stk = deque()
    stk.append((0,0))
    while stk:
        n,ans = stk.popleft()
        for x in gp[n]:
            cnts[x]-=1
            if(cnts[x]==0):
                stk.append((x,ans+1))
                cnt += 1
    if(cnt!=M):
        print(-1)
    else:
        print(ans)

if __name__ == '__main__':
    main()

Buggy python submission (verdict: Time Limit Exceeded):
import sys
sys.setrecursionlimit(1000000)
input = sys.stdin.readline

def combination_to_index(a,b,n):
    if(b<a):
        c = a
        a = b
        b = c
    return (2*n-a)*(a-1)//2+b-a

def dfs(gp):
    max_d = 0
    stk = []
    stk.append((0,set(),0))
    while stk:
        nxt = []
        n,seen,d = stk.pop()
        res = -1
        if(n in seen):
            continue
        max_d = max(max_d,d)
        for x in gp[n]:
            nxt.append((x,seen.union(set([n])),d+1))
        stk = nxt+stk
    return max_d

def main():
    N = int(input())
    M = N*(N-1)//2
    gp = [[] for _ in range(M+1)]
    for a in range(1,N+1):
        A = [int(x) for x in input().split()]
        for ind,b in enumerate(A[:-1]):
            gp[combination_to_index(a,b,N)].append(combination_to_index(a,A[ind+1],N))
    cnts = [0]*(M+1)
    for i in gp:
        for j in i:
            cnts[j]+=1

    for ind,i in enumerate(cnts):
        if(i==0 and ind!=0):
            gp[0].append(ind)

    d = dfs(gp)
    if(d==0):
        print(-1)
    else:
        print(d)

if __name__ == '__main__':
    main()


Fixed submission:
import sys
from collections import deque
input = sys.stdin.readline
def combination_to_index(a,b,n):
    if(b<a):
        a,b = b,a
    return (2*n-a)*(a-1)//2+b-a

def main():
    N = int(input())
    M = N*(N-1)//2
    gp = [[] for _ in range(M+1)]
    cnts = [0]*(M+1)
    for a in range(1,N+1):
        A = [int(x) for x in input().split()]
        for ind,b in enumerate(A[:-1]):
            fr = combination_to_index(a,b,N)
            to = combination_to_index(a,A[ind+1],N)
            gp[fr].append(to)
            cnts[to] += 1

    for ind,i in enumerate(cnts):
        if(i==0 and ind!=0):
            gp[0].append(ind)
            cnts[ind]+=1

    ans = 0
    cnt = 0
    stk = deque()
    stk.append((0,0))
    while stk:
        n,ans = stk.popleft()
        for x in gp[n]:
            cnts[x]-=1
            if(cnts[x]==0):
                stk.append((x,ans+1))
                cnt += 1
    if(cnt!=M):
        print(-1)
    else:
        print(ans)

if __name__ == '__main__':
    main()

Buggy python submission (verdict: Runtime Error):
def combination_to_index(a,b,n):
    if(b<a):
        c = a
        a = b
        b = c
    return (2*n-a)*(a-1)//2+b-a

def dfs(gp):
    max_d = 0
    stk = []
    stk.append((0,set(),0))
    while stk:
        nxt = []
        n,seen,d = stk.pop()
        res = -1
        if(n in seen):
            continue
        max_d = max(max_d,d)
        for x in gp[n]:
            nxt.append((x,seen.union(set([n])),d+1))
        stk = nxt+stk
    return max_d

def main():
    N = int(input())
    M = N*(N-1)//2
    gp = [[] for _ in range(M+1)]
    for a in range(1,N+1):
        A = [int(x) for x in input().split()]
        for ind,b in enumerate(A[:-1]):
            gp[combination_to_index(a,b,N)].append(combination_to_index(a,A[ind+1],N))
    cnts = [0]*(M+1)
    for i in gp:
        for j in i:
            cnts[j]+=1

    for ind,i in enumerate(cnts):
        if(i==0 and ind!=0):
            gp[0].append(ind)

    d = dfs(0,set(),gp,0)
    if(d==0):
        print(-1)
    else:
        print(d)

if __name__ == '__main__':
    main()


Fixed submission:
import sys
from collections import deque
input = sys.stdin.readline
def combination_to_index(a,b,n):
    if(b<a):
        a,b = b,a
    return (2*n-a)*(a-1)//2+b-a

def main():
    N = int(input())
    M = N*(N-1)//2
    gp = [[] for _ in range(M+1)]
    cnts = [0]*(M+1)
    for a in range(1,N+1):
        A = [int(x) for x in input().split()]
        for ind,b in enumerate(A[:-1]):
            fr = combination_to_index(a,b,N)
            to = combination_to_index(a,A[ind+1],N)
            gp[fr].append(to)
            cnts[to] += 1

    for ind,i in enumerate(cnts):
        if(i==0 and ind!=0):
            gp[0].append(ind)
            cnts[ind]+=1

    ans = 0
    cnt = 0
    stk = deque()
    stk.append((0,0))
    while stk:
        n,ans = stk.popleft()
        for x in gp[n]:
            cnts[x]-=1
            if(cnts[x]==0):
                stk.append((x,ans+1))
                cnt += 1
    if(cnt!=M):
        print(-1)
    else:
        print(ans)

if __name__ == '__main__':
    main()

Buggy python submission (verdict: Time Limit Exceeded):
import sys
sys.setrecursionlimit(1000000)

def combination_to_index(a,b,n):
    if(b<a):
        c = a
        a = b
        b = c
    return (2*n-a)*(a-1)//2+b-a

def dfs(n,seen,gp,d):
    #print(d)
    res = -1
    if(n in seen):
        return -1
    for x in gp[n]:
        res = max(res,dfs(x,seen.union(set([n])),gp,d+1))

    if(res == -1):
        return d
    else:
        return res

def main():
    N = int(input())
    M = N*(N-1)//2
    gp = [[] for _ in range(M+1)]
    for a in range(1,N+1):
        A = [int(x) for x in input().split()]
        for ind,b in enumerate(A[:-1]):
            gp[combination_to_index(a,b,N)].append(combination_to_index(a,A[ind+1],N))
    cnts = [0]*(M+1)
    for i in gp:
        for j in i:
            cnts[j]+=1

    for ind,i in enumerate(cnts):
        if(i==0 and ind!=0):
            gp[0].append(ind)

    d = dfs(0,set(),gp,0)
    if(d==0):
        print(-1)
    else:
        print(d)

if __name__ == '__main__':
    main()


Fixed submission:
import sys
from collections import deque
input = sys.stdin.readline
def combination_to_index(a,b,n):
    if(b<a):
        a,b = b,a
    return (2*n-a)*(a-1)//2+b-a

def main():
    N = int(input())
    M = N*(N-1)//2
    gp = [[] for _ in range(M+1)]
    cnts = [0]*(M+1)
    for a in range(1,N+1):
        A = [int(x) for x in input().split()]
        for ind,b in enumerate(A[:-1]):
            fr = combination_to_index(a,b,N)
            to = combination_to_index(a,A[ind+1],N)
            gp[fr].append(to)
            cnts[to] += 1

    for ind,i in enumerate(cnts):
        if(i==0 and ind!=0):
            gp[0].append(ind)
            cnts[ind]+=1

    ans = 0
    cnt = 0
    stk = deque()
    stk.append((0,0))
    while stk:
        n,ans = stk.popleft()
        for x in gp[n]:
            cnts[x]-=1
            if(cnts[x]==0):
                stk.append((x,ans+1))
                cnt += 1
    if(cnt!=M):
        print(-1)
    else:
        print(ans)

if __name__ == '__main__':
    main()

Buggy python submission (verdict: Runtime Error):
def combination_to_index(a,b,n):
    if(b<a):
        c = a
        a = b
        b = c
    return (2*n-a)*(a-1)//2+b-a

def dfs(n,seen,gp,d):
    #print(d)
    res = -1
    if(n in seen):
        return -1
    for x in gp[n]:
        res = max(res,dfs(x,seen.union(set([n])),gp,d+1))

    if(res == -1):
        return d
    else:
        return res

def main():
    N = int(input())
    M = N*(N-1)//2
    gp = [[] for _ in range(M+1)]
    for a in range(1,N+1):
        A = [int(x) for x in input().split()]
        for ind,b in enumerate(A[:-1]):
            gp[combination_to_index(a,b,N)].append(combination_to_index(a,A[ind+1],N))
    cnts = [0]*(M+1)
    for i in gp:
        for j in i:
            cnts[j]+=1

    for ind,i in enumerate(cnts):
        if(i==0 and ind!=0):
            gp[0].append(ind)

    d = dfs(0,set(),gp,0)
    if(d==0):
        print(-1)
    else:
        print(d)

if __name__ == '__main__':
    main()


Fixed submission:
import sys
from collections import deque
input = sys.stdin.readline
def combination_to_index(a,b,n):
    if(b<a):
        a,b = b,a
    return (2*n-a)*(a-1)//2+b-a

def main():
    N = int(input())
    M = N*(N-1)//2
    gp = [[] for _ in range(M+1)]
    cnts = [0]*(M+1)
    for a in range(1,N+1):
        A = [int(x) for x in input().split()]
        for ind,b in enumerate(A[:-1]):
            fr = combination_to_index(a,b,N)
            to = combination_to_index(a,A[ind+1],N)
            gp[fr].append(to)
            cnts[to] += 1

    for ind,i in enumerate(cnts):
        if(i==0 and ind!=0):
            gp[0].append(ind)
            cnts[ind]+=1

    ans = 0
    cnt = 0
    stk = deque()
    stk.append((0,0))
    while stk:
        n,ans = stk.popleft()
        for x in gp[n]:
            cnts[x]-=1
            if(cnts[x]==0):
                stk.append((x,ans+1))
                cnt += 1
    if(cnt!=M):
        print(-1)
    else:
        print(ans)

if __name__ == '__main__':
    main()