COT 5405: Advanced Algorithms
Fall 2006
Assignment 1
Due: 5pm, 29 Sep 2006
1. (20 points) Given the following instance of set cover: sets {a, b}, {a, c, d}, {b, d e}, and
{a, b, e}, with costs 3, 2, 3, and 4 respectively, find the solution using the greedy algorithm
discussed in class. Show all the steps in the algorithm.
2. (20 points) Given the following instance of Knapsack: profits (5, 5, 7, 10, 4), sizes (2, 2,
3, 6, 1), and capacity 7, find an approximate solution yielded by the FTPAS we discussed in
class. Take
= 2, even though you would not do this in a real application. Show all the steps
in the algorithm.
3. (20 points) Given the following instance of set cover: sets {a, b}, {a, c, d}, {b, d e}, and
{a, b, e}, with costs 2, 4, 3, and 3 respectively, find the solution using the primal-dual
algorithm discussed in class. Pick the ys in alphabetical order. Show all the steps in the
algorithm. Note that the costs here are different from those in problem 1.
4. (20 points) Formulate the minimum dominating set problem as an integer linear program.
This problem is defined as follows. Given a graph G = (V, E), find a dominating set of
smallest cardinality. A set V’
V is a dominating set if for each u
V-V’, there exists a
v
V’ such that {u, v}
E.
5. (20 points) (From AA) Consider the following factor 2 approximation algorithm for
cardinality vertex cover on a connected graph. Find a depth first search tree in the given
graph, G, and output the set, say S, of all the non-leaf vertices of this tree. Show that S is a
vertex cover for G and |S| 2 OPT. Hint: Show that G has a matching of size at least |S|/2.