Codeforces Round #203(Div. 2)B. Resort

B. Resort

time limit per test

2 seconds

memory limit per test

256 megabytes

input

standard input

output

standard output

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 nobjects (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:

1. Objects with numbers v1, v2, ..., vk - 1 are mountains and the object with number vk is the hotel.
2. For any integer i (1 ≤ i < k), there is exactly one ski track leading from object vi. This track goes to object vi + 1.
3. 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 thei-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 numberai 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 test(s)

input

50 0 0 0 10 1 2 3 4

output

51 2 3 4 5

input

50 0 1 0 10 1 2 2 4

output

24 5

input

41 0 0 02 3 4 2

output

11

题目大意：给你两组数，第一组：0表示山，1表示宾馆。第二组：表示第i个点与第a[i]个点是相连的。求：一条路径，有且只有终点是宾馆，并且为了不迷路，所选取的点只有一条路可走。

题目分析：既然给了最后一定是宾馆，暴力，找到每一个宾馆，然后倒序找回去，注意退出条件即可。

AC代码：

#include<cstdio>#include<cstring>const int mmax=100005;int ss[mmax],map[mmax];int ok[mmax],ans[mmax];int path[mmax];int main(){    int n;    while(scanf("%d",&n)!=EOF)    {        memset(ok,0,sizeof ok);        for(int i=1;i<=n;i++)            scanf("%d",&ss[i]);        for(int i=1;i<=n;i++)        {            scanf("%d",&map[i]);            ok[map[i]]++;                  ///记录这个点是否是单条路线的点        }        int anse=0;        for(int i=1;i<=n;i++)        {            if(ss[i]==1)            {                int e=0,t=i;                path[e++]=t;                while(map[t]!=0 && ok[map[t]]<2)    ///两个退出条件                {                    path[e++]=map[t];                    t=map[t];                }                if(e>anse)                {                    anse=e;                    for(int j=0;j<anse;j++)                        ans[j]=path[j];                }            }        }        printf("%d\n",anse);        for(int i=anse-1;i>=0;i--)            printf("%d ",ans[i]);        puts("");    }    return 0;}