Check if a given tree graph is linear or not in C++

Here we will see how to check whether a tree graph is linear or not. A linear tree graph can be expressed in one line, suppose this is an example of a linear tree graph.

But this is not linear −

To check a graph is linear or not, we can follow two conditions

• If the number of nodes is 1, then the tree graph is linear
• If (n – 2) of its nodes have in-degree 2

Example

 Live Demo

#include <iostream>
#include <vector>
#define N 4
using namespace std;
class Graph{
   private:
   int V;
   vector<int> *adj;
   public:
   Graph(int v){
      V = v;
      adj = new vector<int>[v];
   }
   void addEdge(int u, int v){
      adj[u].push_back(v);
      adj[v].push_back(u);
   }
   bool isLinear() {
      if (V == 1)
         return true;
      int count = 0;
      for (int i = 0; i < V; i++) {
         if (adj[i].size() == 2)
         count++;
      }
      if (count == V - 2)
         return true;
      else
         return false;
   }
};
int main() {
   Graph g1(3);
   g1.addEdge(0, 1);
   g1.addEdge(0, 2);
   if (g1.isLinear())
      cout << "The graph is linear";
   else
      cout << "The graph is not linear";
}

Output

The graph is linear