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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. vector<vector<int>> adj;
  5. vector<int> dp;        
  6. vector<int> euler;     
  7. vector<int> tin;       
  8.  
  9. void dfs(int node, int par) {
  10.     tin[node] = euler.size();
  11.     euler.push_back(node);
  12.  
  13.     dp[node] = 1;
  14.  
  15.     for (int child : adj[node]) {
  16.         if (child != par) {
  17.             dfs(child, node);
  18.             dp[node] += dp[child];
  19.         }
  20.     }
  21. }
  22.  
  23. int main() {
  24.     int m;
  25.     cin >> m;
  26.  
  27.     adj.resize(m + 1);
  28.     dp.resize(m + 1);
  29.     tin.resize(m + 1);
  30.  
  31.     for (int i = 0; i < m - 1; i++) {
  32.         int u, v;
  33.         cin >> u >> v;
  34.         adj[u].push_back(v);
  35.         adj[v].push_back(u);
  36.     }
  37.  
  38.     // sort children
  39.     for (int i = 1; i <= m; i++) {
  40.         sort(adj[i].begin(), adj[i].end());
  41.     }
  42.  
  43.     // Euler DFS
  44.     dfs(1, 0);
  45.  
  46.     int q;
  47.     cin >> q;
  48.  
  49.     while (q--) {
  50.         int n, k;
  51.         cin >> n >> k;
  52.  
  53.         if (k > dp[n]) {
  54.             cout << -1 << "\n";
  55.         } else {
  56.             cout << euler[tin[n] + k - 1] << "\n";
  57.         }
  58.     }
  59.  
  60.     return 0;
  61. }
  62.  
Success #stdin #stdout 0.01s 5276KB
comments (?)
stdin
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7
1 2
1 3
2 4
2 5
3 6
3 7
6
1 1
1 4
2 3
3 2
4 1
3 5
stdout
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1
5
5
6
4
-1
https://ideone.com/DJl1GS
language:
C++14 (gcc 8.3)
created:
3 days ago
visibility:
public

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