## Description

Analysis of Algorithms

(Computer Science 340b)

ASSIGNMENT 3

1. Modify the KMP string matching algorithm to find the largest prefix of P that matches

a substring of T. In other words, you do not need to match all of P inside T; instead, you

want to find the largest match (but it has to start with p1).

2. In the textbook, 15.4-2 (pp. 396).

3. In the textbook, 16.2-5 (pp. 428).

4. In the textbook, 16.3-8 (pp. 436).

5. Solve the following variation of the 0-1 knapsack problem (pp. 425): The assumptions

are identical to those of the 0-1 knapsack problem, except that there is an unlimited supply

of each item. In other words, the problem is to pack of maximum value with items of given

weights and values in a knapsack with a given-weight, but each item may appear many times.

6. Modify minimum spanning tree algorithm to find maximum spanning tree.

7. Find a counter example with three vertices that shows Dijkstra’s algorithm does not work

when there is negative weight edge.

8. Let G = (V, E) be a weighted directed graph with no negative cycle. Design an algorithm

to find a cycle in G with minimum weight. The algorithm should run in time O(|V |

3

).

9. Implement the Dijkstra’s single source shortest path algorithm for a weighted directed

graph using a heap data structure. The time complexity of the algorithm should be O((|V |+

|E|) log |V |).

A heap data structure for peiority queue (check notes ”Heaps” from page 9 for priority

queue) should be implemented as an abstract data type (a class in C++, Java, or Python)

on a set of elements, where each element has an id and a key, with the following operations.

1

• heap(keys, n): initializes a heap with the array keys of n elements.

• in heap(id): returns true if the element whose id is id is in the heap;

• min key(): returns the minimum key of the heap;

• min id(): returns the id of the element with minimum key in the heap;

• key(id): returns the key of the element whose id is id in the heap;

• delete min(): deletes the element with minimum key from the heap;

• decrease key(id, new key): sets the key of the element whose id is id to new key if its

current key is greater than new key.

An input graph file will be available. The format of the input file is the following:

• The first line of the input file contains an integer, n, indicating the number of vertices

of the input graph.

• Each of the remaining lines contains a triple “i j w”, where 1 ≤ i, j ≤ n, indicating an

edge from vertex i to vertex j with weight w.

Vertex 1 is considered as the source.

The output of your program should be the following:

• The input graph in adjacency list representation: Print the adjacency lists in any

reasonable format. Print each edge with its weight.

• The shortest path tree edges with shortest path weights: The edges should be listed in

the order in which they are produced by the Dijkastra’s algorithm. For each shortest

path tree edge (i, j), print “(i, j) : w” in a separate line, where w is the shortest path

weight from the source to vertex j.

In your gaul account, you should create a directory called ”asn3” which contains your

Assignment Submission Form, asn3 solution.pdf for question 1 to question 8, your

program for question 9, the input file with name infile, and a makefile. The makefile

should be written such that the command ”make clean” will remove all the ”*.o” files and

the command ”make” will generate an executable file asn3 that can be run by typing ”asn3

< infile”. If you are using Java or Python, you may not need the makefile. In that case,

you should have a script file, asn3, so that by typing ”asn3 < infile” your Java or Python

program will run.

You should use script command to capture the screen of the execution of your program.

The resulting file should also be in directory ”asn3”.

Your programs have to be able to run on compute.gaul.csd.uwo.ca as our TAs will be

marking your programs with this machine.

Once ready, create a tar file for directory ”asn3” and submit the tar file through OWL

course website assignment 3 area. Please check assignment submission guideline for details.

2

• To answer a question for designing an algorithm, the following three steps are needed

1. Describe your algorithm in English (not with pseudo code);

2. Show why the algorithm is correct; and

3. Analyse the complexity of the algorithm.

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