Resort (Codeforces 350B)
Tags: Others, graphs

Valera's finally decided to go on holiday! He packed up and headed for a ski resort.Valera's fancied a ski trip but he soon realized that he could get lost in this new place. Somebody gave him a useful hint: the resort has n objects (we will consider the objects indexed in some way by integers from 1 to n), each object is either a hotel or a mountain.Valera has also found out that the ski resort had multiple ski tracks. Specifically, for each object v, the resort has at most one object u, such that there is a ski track built from object u to object v. We also know that no hotel has got a ski track leading from the hotel to some object.Valera is afraid of getting lost on the resort. So he wants you to come up with a path he would walk along. The path must consist of objects v1, v2, ..., vk (k ≥ 1) and meet the following conditions:  Objects with numbers v1, v2, ..., vk - 1 are mountains and the object with number vk is the hotel.  For any integer i (1 ≤ i < k), there is exactly one ski track leading from object vi. This track goes to object vi + 1.  The path contains as many objects as possible (k is maximal). Help Valera. Find such path that meets all the criteria of our hero!

Input: The first line contains integer n (1 ≤ n ≤ 105) — the number of objects.The second line contains n space-separated integers type1, type2, ..., typen — the types of the objects. If typei equals zero, then the i-th object is the mountain. If typei equals one, then the i-th object is the hotel. It is guaranteed that at least one object is a hotel.The third line of the input contains n space-separated integers a1, a2, ..., an (0 ≤ ai ≤ n) — the description of the ski tracks. If number ai equals zero, then there is no such object v, that has a ski track built from v to i. If number ai doesn't equal zero, that means that there is a track built from object ai to object i.

Output: In the first line print k — the maximum possible path length for Valera. In the second line print k integers v1, v2, ..., vk — the path. If there are multiple solutions, you can print any of them.


Sample Inputs:
5
0 0 0 0 1
0 1 2 3 4

5
0 0 1 0 1
0 1 2 2 4

4
1 0 0 0
2 3 4 2

Sample Outputs:
5
1 2 3 4 5

2
4 5

1
1

Solution (Python):
n = int(input())
t = [0] + list(map(int, input().split()))
a = [0] + list(map(int, input().split()))
(ans, cnt) = ([], [0 for i in range(n + 1)])
for i in a:
    cnt[i] += 1
for i in range(1, n + 1):
    if t[i] == 1:
        crt = [i]
        x = a[i]
        while cnt[x] == 1:
            crt.append(x)
            x = a[x]
        if len(crt) > len(ans):
            ans = crt[:]
ans.reverse()
print(len(ans))
print(' '.join(map(str, ans)))

Solution (Python):
n = int(input())
(list_a, list_b) = ([0] + list(map(int, input().split())), [0] + list(map(int, input().split())))
(result, p) = ([], [0] * (n + 1))
for i in list_b:
    p[i] += 1
for i in range(1, n + 1):
    if list_a[i] == 1:
        temp_list = [i]
        x = list_b[i]
        while p[x] == 1:
            temp_list.append(x)
            x = list_b[x]
        if len(temp_list) > len(result):
            result = temp_list[:]
result.reverse()
print(len(result))
print(' '.join((str(x) for x in result)))

Solution (Python):
n = int(input())
t = [0] + list(map(int, input().split()))
a = [0] + list(map(int, input().split()))
(ans, cnt) = ([], [0 for i in range(n + 1)])
for i in a:
    cnt[i] += 1
for i in range(1, n + 1):
    if t[i] == 1:
        crt = [i]
        x = a[i]
        while cnt[x] == 1:
            crt.append(x)
            x = a[x]
        if len(crt) > len(ans):
            ans = crt[:]
ans.reverse()
print(len(ans))
print(' '.join(map(str, ans)))