Codeforces Round #203 (Div. 2) B Resort

// Codeforces Round #203 (Div. 2) B Resort
// Problem: http://codeforces.com/contest/350/problem/B

import java.io.*;
import java.math.*;
import java.util.*;

//Codeforces
public class MainCodeforces1 {
private static MyScanner in;
private static PrintStream out;
private static boolean LOCAL_TEST = false;

private static void solve() throws IOException
{
int n = in.nextInt();
int[] type = new int[n + 1];
int[] a = new int[n + 1];
int[] na = new int[n + 1];
for (int i = 1; i <= n; i++) {
type[i] = in.nextInt();
}
for (int i = 1; i <= n; i++) {
a[i] = in.nextInt();
if (a[i] > 0)
na[a[i]]++;
}
int maxLength = 0;
ArrayList<Integer> bestList = new ArrayList<Integer>();
for (int i = 1; i <= n; i++) {
if (type[i] == 0)
continue;
ArrayList<Integer> list = new ArrayList<Integer>();
int p = i;
list.add(p);
while (true) {
p = a[p];
if (na[p] == 0 || na[p] > 1)
break;
else {
if (type[p] == 0)
list.add(p);
else
break;
}
}
if (list.size() > maxLength) {
maxLength = list.size();
bestList = list;
}
}
out.println(bestList.size());
StringBuilder sb = new StringBuilder();
for (int j = bestList.size() - 1; j >= 0; j--) {
sb.append(bestList.get(j).toString());
if (j > 0)
sb.append(" ");
}
out.println(sb);
}

public static void main(String[] args) throws IOException {
// helpers for input/output
out = System.out;
try {
String cname = System.getenv("COMPUTERNAME");
if (!cname.equals(""))
LOCAL_TEST = true;
} catch (Exception e) {
}
if (LOCAL_TEST) {
in = new MyScanner("E:\\zin.txt");
}
else {
boolean usingFileForIO = false;
if (usingFileForIO) {
// using input.txt and output.txt as I/O
in = new MyScanner("input.txt");
out = new PrintStream("output.txt");
}
else {
in = new MyScanner();
out = System.out;
}
}

solve();
}

// =====================================
static class MyScanner {
BufferedReader bufReader;
StringTokenizer strTok;

public MyScanner() throws IOException
{
bufReader = new BufferedReader(new InputStreamReader(System.in));
strTok = new StringTokenizer("");
}

public MyScanner(String inputFile) throws IOException {
bufReader = new BufferedReader(new InputStreamReader(new FileInputStream(
inputFile)));
strTok = new StringTokenizer("");
}

String GetNextToken() throws IOException {
if (!strTok.hasMoreTokens())
strTok = new StringTokenizer(bufReader.readLine());
return strTok.nextToken();
}

public int nextInt() throws IOException {
return Integer.valueOf(GetNextToken());
}

public long nextLong() throws IOException {
return Long.valueOf(GetNextToken());
}

public double nextDouble() throws IOException {
return Double.valueOf(GetNextToken());
}

public String nextString() throws IOException {
return GetNextToken();
}

public String nextLine() throws IOException {
return bufReader.readLine();
}

public int countTokens() {
return strTok.countTokens();
}

public boolean hasMoreTokens() {
return strTok.hasMoreTokens();
}
}

}