3. Consider the activity selection problem as discussed in class where we are given n intervals (21, 31),..., (n. Yn) and we would like to select a maximum number of pairwise disjoint intervals. Consider the following greedy algorithm for this problem: Algorithm 1 Activity Selection((x₁, y₁),..., (En, Yn)) A = {1,...,n} S-0 while A # ) do Pick i € A that minimizes |{j € A | (xi, yi) (xj, yj) #0}| breaking ties arbitrarily interval has smallest number of intersections S SU{i} ▷ i-th A+ A- {i} A+ A-{je A | (xi, yi) (x, yj) #0} > Removes i and all its intersecting intervals from A end while return(S) Prove or disprove that this greedy algorithm always outputs the optimal answer. To disprove you would need to provide a counter-example. To prove you need to prove that for all possible inputs it provides the optimal answer.

Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
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Solve by  greedy algorithm

3.
Consider the activity selection problem as discussed in class where we are given n
intervals (1,91), ..., (En, Yn) and we would like to select a maximum number of pairwise disjoint
intervals. Consider the following greedy algorithm for this problem:
Algorithm 1 Activity Selection((x₁, y₁),..., (En, Yn))
A = {1,...,n}
S + Ø
while A # 0 do
Pick i € A that minimizes |{j € A | (xi, Yi) (xj, Yj) #0}| breaking ties arbitrarily ▷ i-th
interval has smallest number of intersections
S + SU {i}
A+ A- {i}
A+ A-{je A | (xi, yi) (xj, Yj) # 0} ▷ Removes i and all its intersecting intervals from A
end while
return(S)
Prove or disprove that this greedy algorithm always outputs the optimal answer. To disprove
you would need to provide a counter-example. To prove you need to prove that for all possible
inputs it provides the optimal answer.
Transcribed Image Text:3. Consider the activity selection problem as discussed in class where we are given n intervals (1,91), ..., (En, Yn) and we would like to select a maximum number of pairwise disjoint intervals. Consider the following greedy algorithm for this problem: Algorithm 1 Activity Selection((x₁, y₁),..., (En, Yn)) A = {1,...,n} S + Ø while A # 0 do Pick i € A that minimizes |{j € A | (xi, Yi) (xj, Yj) #0}| breaking ties arbitrarily ▷ i-th interval has smallest number of intersections S + SU {i} A+ A- {i} A+ A-{je A | (xi, yi) (xj, Yj) # 0} ▷ Removes i and all its intersecting intervals from A end while return(S) Prove or disprove that this greedy algorithm always outputs the optimal answer. To disprove you would need to provide a counter-example. To prove you need to prove that for all possible inputs it provides the optimal answer.
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