# CSC-141: Assignment 2

Instructor: Michalis Faloutsos

## Due on:  Monday Nov. 1st, 1999: 11:59 pm.

This assignment has only a programming part.

1. [25]. Implement the class Tree.  Often given a graph, we end up finding a tree. Tree is also a graph with the addition of  the relationship "parent": for every node we need to know the parent.  In our case, we can have a field of the class to point to the graph that corresponds to the tree or  the original graph from which we calculated the tree. The root of the tree has no parent, and this we will denote by the constant NONE which will be equal to "-1". We want to have the following methods:

setParent(node-id, parent-node-id)
getParent(node-id) ,   return parent-node-id
findChildren(node-id),    return an array of children
print(), print the tree

Partial Marks [-10]: The printing of the tree could be a simple output of the  child-parent pairs.

Full Marks : The printing of the tree should be in a breadth first way by generation (hop distance from the root) and in the form:  parent -> child

Assume the tree:

root -- node1  -- node3
|                     \-- node4
|
|-- node2  -- node5

The  output should look like:

0: root
1:  root  -> node1
1:  root  -> node2
2:  node1 -> node3
2:  node1 -> node4
2:  node2 -> node5

Tip: we can use a simple array or linked-list to keep track of the parent information as we have said in class.

2. [50]. Implement Dijkstra's algorithm for shortest paths.  You will read a directed weighted graph with positive weights.  The  source/root node is  kept in the field "Source" and of the class with a default value of the first node-id that you read from the input file.

The output is:
2.a. The COST of the  shortest path between the source and every node.
2.b. The shortest path tree (with the print() method you have implemented in the previous question).

3. [25]. Implement Prim's algorithm for minimum spanning trees. Here you can assume that the graph is undirected.

The output is:
3.a. The total cost of the minimum spanning tree.
3.b. The minimum spanning tree (with your print() method).

Tip: Note that the Prim and Dijkstra algorithms have very similar structure and the main difference is the "criterion of selecting the next node". Try to take advantage of that to avoid retyping  the same code.  Some careful planning may be needed though.
The user should be able to choose which algorithm  (tree printing, Prim, Dijkstra) to run.
This could be done through the use of an integer variable (1,2,3) correspondingly.

This is the easiest way to have input output, and it will help the grader test your programs in a uniform way.
Your program (i.e.  myprog) should run as follows:
run < file
where file contains all the data needed to run the program.
The first integer of the file should be the choice of the algorithm.
The rest should be the graph data as before plus the weight of each edge:

2                                          // for Dijkstra
30
1     2     103                     //   node with id : 1 gets to be the root
2     3     110
2     1     150
.........
n1     n2    weight

Also, again your program should be in multiple files and compiling with a makefile.

## Again: you should submit a small write-up of what you did and how no more than 1.5 pages.

Sample Data

Tree Data:
1
5
1   2         1
2   1         1
2    3        1
3    2        1
2    4        1
4    2        1
3    5        1
5    3        1

Prim's
1
5
1   2         1
2   1         1
2    3        10
3    2        10
2    4        11
4    2        11
1     4         20
4     1         20
3    5        13
5    3        13