Given three integers N, D and K. The task is to check whether it is possible to make a tree with exactly N vertices, D diameter (the number of edges in the longest path between any two vertices), and degree of each vertex must be at most K. If it is possible then print all the possible edges otherwise print No.
Input: N = 6, D = 3, K = 4
Input: N = 6, D = 2, K = 4
Approach: Let’s construct the tree with the following algorithm: If (d > n – 1), print “No” and terminate the program. Otherwise, let’s keep the array deg of the length n which will represent degrees of vertices.
The first step is to construct the diameter of the tree. Let the first (d + 1) vertices form it.
Let’s add d edges to the answer and increase degrees of vertices corresponding to these edges, and if some vertex has degree greater than k, print “No” and terminate the program.
The second (and the last) step is to attach the remaining (n – d – 1) vertices to the tree. Let’s call the vertex free if its degree is less than k. Also, let’s keep all free vertices forming the diameter in some data structure which allows us to take the vertex with the minimum maximal distance to any other vertex and remove such vertices. It can be done by, for example, set of pairs (distv, v), where distv is the maximum distance from the vertex v to any other vertex. Now let’s add all the vertices starting from the vertex (d + 1) (0-indexed) to the vertex n?1, let the current vertex be u. One can get the vertex with the minimum maximal distance to any other vertex, let it be v. Now increase the degree of vertices u and v, add the edge between them, and if v still be free, return it to the data structure, otherwise remove it. The same with the vertex u (it is obvious that its maximal distance to any other vertex will be equal to (distv + 1).
If at any step our data structure will be empty or the minimum maximal distance will equal d, the answer is “No”. Otherwise, we can print the answer.
Below is the implementation of the above approach:
1 2 2 3 3 4 5 2 6 2
- Possible edges of a tree for given diameter, height and vertices
- Minimum Operations to make value of all vertices of the tree Zero
- Find the cordinates of the fourth vertex of a rectangle with given 3 vertices
- Diameter of n-ary tree using BFS
- Diameter of a tree using DFS
- Diameter of an N-ary tree
- DP on Trees | Set-3 ( Diameter of N-ary Tree )
- Diameter of a Binary Tree
- Diameter of a Binary Tree in O(n) [A new method]
- Spanning Tree With Maximum Degree (Using Kruskal's Algorithm)
- Maximize the sum of products of the degrees between any two vertices of the tree
- Find the number of distinct pairs of vertices which have a distance of exactly k in a tree
- Count the nodes of the tree which make a pangram when concatenated with the sub-tree nodes
- Make Binary Search Tree
- Maximum edge removal from tree to make even forest
If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to firstname.lastname@example.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.