Given an array of time intervals (start, end) for classroom lectures (possibly overlapping), find the minimum number of rooms required. For example, given [(30, 75), (0, 50), (60, 150)], you should return 2.

daily-coding-problem-21.rb

# Sort jobs by finish times so that f1<=f2<=..<=fn
# 𝐴 ← ∅, 𝑙𝑎𝑠𝑡 ← 0
# for 𝑗 ← 1 to 𝑛
#     if 𝑠𝑗 ≥ 𝑙𝑎𝑠𝑡 then 𝐴 ← 𝐴 ∪ {𝑗}, 𝑙𝑎𝑠𝑡 ← 𝑓𝑗
# return �

require('set')

def minimum_room_no(times)
    times = times.sort {|a,b| a[1] <=> b[1]}
    a = Set.new
    last = 0 
    times.each do |t|
        if t[0] >= last
            a = a | [t].to_set()
            last = t[1]
        end 
    end 
    return a.length
end 

times = [[30, 75], [0, 50], [60, 150]]
puts "Minimum Room Number: #{minimum_room_no(times)}"