思路:先dfs找出最长的路劲,再dfs取最长路劲的节点
#include<algorithm>
#include<set>
#include<vector>
#include<queue>
#include<cmath>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<set>
#include<vector>
#include<queue>
#include<cmath>
#include<cstring>
#include<cstdio>
#include<map>
#include<stack>
#include<string>
using namespace std;
#define sfi(i) scanf("%d",&i)
#define pri(i) printf("%d\n",i)
#define sff(i) scanf("%lf",&i)
#define ll long long
#define mem(x,y) memset(x,y,sizeof(x))
#define INF 0x3f3f3f3f
#define eps 1e-6
#define PI acos(-1)
#define lowbit(x) ((x)&(-x))
#define zero(x) (((x)>0?(x):-(x))<eps)
#define fl() printf("flag\n")
ll gcd(ll a,ll b){while(b^=a^=b^=a%=b);return a;}
const int maxn=1e5+9;
const int mod=9973;
template <class T>
inline void sc(T &ret)
{
char c;
ret = 0;
while ((c = getchar()) < '0' || c > '9');
while (c >= '0' && c <= '9')
{
ret = ret * 10 + (c - '0'), c = getchar();
}
}
int n;
vector<int>g[maxn],ans;
int st;
int Max=0;
void dfs1(int u,int cnt)
{
Max=max(Max,cnt);
for(int i=0;i<g[u].size();i++)
{
dfs1(g[u][i],cnt+1);
}
}
void dfs2(int u,int cnt)
{
if(cnt==Max)
{
ans.push_back(u);
return ;
}
for(int i=0;i<g[u].size();i++)
{
dfs2(g[u][i],cnt+1);
}
}
int main()
{
cin>>n;
for(int i=1;i<=n;i++)
{
int x;
cin>>x;
if(x!=-1)
g[x].push_back(i);
else st=i;
}
dfs1(st,1);
dfs2(st,1);
cout<<Max<<endl;
for(int i=0;i<ans.size();i++)
{
if(i!=0) cout<<" ";
cout<<ans[i];
}
return 0;
}