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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int main() {
  5.     int n;
  6.     cin >> n;
  7.  
  8.     vector<vector<int>> graph(n);
  9.  
  10.     for (int i = 0; i < n - 1; i++) {
  11.         int x, y;
  12.         cin >> x >> y;
  13.         x--, y--;
  14.         graph[x].push_back(y);
  15.         graph[y].push_back(x);
  16.     }
  17.  
  18.     if (graph[0].size() <= 2) {
  19.         cout << "Tree can stay rooted at the current root! 1\n";
  20.         return 0;
  21.     }
  22.  
  23.     for (int i = 1; i < n; i++) {
  24.         if (graph[i].size() <= 2) {
  25.             cout << "Tree should be rerooted to " << i + 1 << "\n";
  26.             return 0;
  27.         }
  28.     }
  29.  
  30.     cout << "No valid root exists\n";
  31.     return 0;
  32. }
  33.  
Success #stdin #stdout 0.01s 5276KB
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5
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1 3
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stdout
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Tree should be rerooted to 2
https://ideone.com/ictFlg
language:
C++ (gcc 8.3)
created:
9 days ago
visibility:
public

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