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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.     if (n == 1) {
  9.         return 0;
  10.         // if the tree has 1 node. the question is already solved.
  11.     }
  12.  
  13.     vector<vector<int>> adj(n + 1);
  14.  
  15.     for (int i = 0; i < n - 1; ++i) {
  16.         int u, v;
  17.         cin >> u >> v;
  18.         adj[u].push_back(v);
  19.         adj[v].push_back(u);
  20.     }
  21.  
  22. 	int root; 
  23. 	cin >> root;
  24.  
  25. 	if(adj[root].size() <= 2){
  26. 		return 0;
  27. 		// if the root has less than or equal to two nodes it also means that the question is solved.
  28. 	}
  29.  
  30.  
  31.     bool found_leaf = false;
  32.     for (int i = 1; i <= n; ++i) {
  33.  
  34.         if (adj[i].size() == 1) {
  35.             cout << "The leaf node which is now root node: "<< i << endl;
  36.             root = i;
  37.             found_leaf = true;
  38.             break; 
  39.         }
  40.     }
  41.  
  42.     if (!found_leaf) {
  43.         cout << "Invalid Tree" << endl;
  44.     }
  45.  
  46.     return 0;
  47. }
Success #stdin #stdout 0s 5312KB
comments (?)
stdin 
5
1 2
1 3
1 4
2 5
1
stdout 
The leaf node which is now root node: 3
https://ideone.com/tnMWCm
language:
C++14 (gcc 8.3)
created:
4 days ago
visibility:
public

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