https://codeforces.com/contest/1143/problem/C

题解：DFS 

/*
*@Author:   STZG
*@Language: C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
#define endl "\n"
using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=100000+10;
const int M=100000+10;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
int t,n,m,k,p,l,r,u,v;
int ans[N],cnt,flag,temp,sum;
int pre[N];
int a[N];
bool vis[N];
char str;
struct node{};
vector<int>G[N];
stack<int>st;
void dfs(int u){
    vis[u]=1;
    bool res=1;
    for(int i=0,j=G[u].size();i<j;i++){
        int v=G[u][i];
        if(!vis[v]){

            res&=a[v];
            dfs(v);
        }

    }
    if(res&&a[u]){
        ans[++cnt]=u;
    }
}
int main()
{
#ifdef DEBUG
	freopen("input.in", "r", stdin);
	//freopen("output.out", "w", stdout);
#endif
    //ios::sync_with_stdio(false);
    //cin.tie(0);
    //cout.tie(0);
    //scanf("%d",&t);
    //while(t--){
    scanf("%d",&n);
    int root;
    for(int i=1;i<=n;i++){
        scanf("%d%d",&v,&a[i]);
        if(v==-1){
            root=i;
            a[i]=0;
        }else{
            G[v].push_back(i);
        }
    }
    for(int i=1;i<=n;i++)
        sort(G[i].begin(),G[i].end());
    dfs(root);
    if(cnt==0){
        cout<<-1<<endl;
        return 0;
    }else{
        sort(ans+1,ans+cnt+1);
        for(int i=1;i<=cnt;i++)
            printf("%d%c",ans[i]," \n"[i==cnt]);
    }

    //}

#ifdef DEBUG
	printf("Time cost : %lf s\n",(double)clock()/CLOCKS_PER_SEC);
#endif
    //cout << "Hello world!" << endl;
    return 0;
}