PTA满树遍历求助--有个测试点错了

#include<bits/stdc++.h>
using namespace std;
vector<int> pre;
void dfs(vector<int>&arr, int i) {
    int n = arr.size();
    pre.push_back(i+1);
    for (int j = 0; j < n; j++) {
        if (arr[j] == i+1) {
            dfs(arr, j);
        }
    }
}
int main() {
    ios::sync_with_stdio(false);
    cin.tie(NULL);
    int num, n,key;
    vector<int> ori;
    cin >> n;
    int start = 0;
    unordered_map<int,int> mymap;
    for (int i = 0; i < n; i++) {
        cin >> num;
        if(!mymap.count(num)){
            mymap[num]=1;
        }
        else{
            mymap[num]++;
        }
        if (num == 0) { start = i; }
        ori.push_back(num);
    }
    int max=0;
    int check_num=0;
    int check=0;
    for(const auto & pairs:mymap){
        max=pairs.second>max ?pairs.second : max;
        if(pairs.first!=0){
            if(check_num==0)
            check_num=pairs.second;
            else{
                if(check_num != pairs.second){
                    check=1;
                }
                }
        }
    }
    cout<<max<<" ";
    if(check==1){
        cout<<"no"<<endl;
    }
    else{
        cout<<"yes"<<endl;
    }
    dfs(ori, start);
    for (int i = 0; i < n-1; i++) {
        cout << pre[i] << " ";
    }
    cout<<pre[n-1]<<endl;
    return 0;
}

超时问题已经可以解决，想知道答案错误的是哪个测试点。