Challenge: Check if a Given Undirected Graph is Tree or not?

Problem statement

Here’s the basic difference between a graph and a tree. A graph can only be a tree under two conditions:

• There are no cycles.
• The graph is connected.

A graph is connected when there is a path between every pair of vertices. In a connected graph, there are no unreachable vertices. Each vertex must be connected to every other vertex through either a direct edge or a graph traversal.

You have to implement is_tree() function which will take a graph as an input and find out if it is a tree.

Input

An undirected graph.

Output

Returns True if the given graph is a tree. Otherwise, it returns False.

Sample input

graph = {
    0 - 1
    0 - 2
    0 - 3
    3 - 4  
}

Sample output

True

Take a look at the illustration below to understand better.