Codeforces Round #203 (Div. 2)B

来源：互联网发布：source linux命令编辑：程序博客网时间：2024/05/18 00:06

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, ..., v_k (k ≥ 1) and meet the following conditions:

Objects with numbers v₁, v₂, ..., v_k - 1 are mountains and the object with number v_k is the hotel.
For any integer i (1 ≤ i < k), there is exactly one ski track leading from object v_i. This track goes to object v_i + 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, ..., type_n — the types of the objects. If type_i equals zero, then thei-th object is the mountain. If type_i 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, ..., a_n (0 ≤ a_i ≤ n) — the description of the ski tracks. If numbera_i equals zero, then there is no such object v, that has a ski track built from v to i. If number a_i doesn't equal zero, that means that there is a track built from object a_i 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, ..., v_k — 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

看了半天没看懂什么意思。。。

题意：求一条最长的路，终点是旅馆，要求路上的联通杜小于等于2

下面是代码：

#include<iostream>#include<vector>#include<cstring>using namespace std;const int MAX_N=100100;int N;int degree[MAX_N],to[MAX_N],hotel[MAX_N];void solve(){    int ans=0,pre;    vector<int> path,ans1;    for(int i=1;i<=N;i++)    {        if(hotel[i])        {            path.clear();            path.push_back(i);            pre=to[i];            while(pre&°ree[pre]<=2)            {                path.push_back(pre);                pre=to[pre];            }            //if(degree[pre]<=2)              //  path.push_back(pre);        }        if(path.size()>ans)        {            ans=path.size();            ans1=path;        }    }    cout<<ans<<endl;    cout<<ans1[ans1.size()-1];    for(int i=ans1.size()-2;i>=0;i--)        cout<<' '<<ans1[i];    cout<<endl;}int main(){    while(cin>>N)    {        memset(degree,0,sizeof(degree));        memset(to,0,sizeof(to));        for(int i=1;i<=N;i++)           cin>>hotel[i];        for(int i=1;i<=N;i++)        {            cin>>to[i];            degree[i]++;            degree[to[i]]++;        }        solve();    }    return 0;}