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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. int dfs(std::vector<bool>& vis, int ci, vector<int>& v,  vector<vector<int>>& list,unordered_map<int,int> & lenc){
  4.     vis.at(ci)=1;
  5.     v.push_back(ci);
  6.     int uji=-1;
  7.     int l=-1;
  8.     for(int i=0;i<(int)list.at(ci).size();i++){
  9.         if(vis.at(list.at(ci).at(i))==0){
  10.             l=1;
  11.         uji= dfs(vis,list.at(ci).at(i),v,list,lenc);
  12.         }
  13.     }
  14.     if(l==-1) {lenc.at(ci)=ci; return ci;}
  15.     lenc.at(ci)=uji;
  16.     return uji;
  17. }
  18. int main() {
  19.     int n,q;
  20.     scanf("%d%d",&n,&q);
  21.     vector<vector<int>> list(n+1);
  22.     for(int  i=2;i<=n;i++){
  23.         int a;
  24.         scanf("%d",&a);
  25.         list.at(a).push_back(i);
  26.         list.at(i).push_back(a);
  27.     }
  28.     for(int i=1;i<=n;i++){
  29.         sort(list.at(i).begin(),list.at(i).end());
  30.     }
  31.     unordered_map<int,int> lenc;
  32.     vector<int>  v;
  33.     std::vector<bool> vis(1+n, false);
  34.     dfs(vis,1,v,list,lenc);
  35.    unordered_map<int,int> m;
  36.  
  37.    for(int i=0;i<(int)v.size();i++){
  38.        m[v[i]]=i;
  39.    }
  40.  
  41.    while(q--){
  42.        int a,b;
  43.        cin>>a>>b;
  44.        int i1=m.at(a);
  45.        int i2=m.at(lenc.at(a));
  46.        if(i1+b-1>i2) printf("-1\n");
  47.        else printf("%d\n",v.at(i1+b-1));
  48.    }
  49. }
Runtime error #stdin #stdout #stderr 0s 4392KB
comments (?)
stdin
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9 6
1 1 1 3 5 3 5 7
3 1
1 5
3 4
7 3
1 8
1 9
stdout
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Standard output is empty
stderr
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terminate called after throwing an instance of 'std::out_of_range'
  what():  _Map_base::at
https://ideone.com/D73rSn
language:
C++14 (gcc 8.3)
created:
6 years ago
visibility:
secret

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