Carlos

sql

clients
 - id
 - email

client_plans
 - id
 - client_id
 - plan_id
 - date_started
 - date_ended

plans
 - id
 - name
 - price
 
 
 
 Plans:
 1,"small",$10
 
 Clients:
 1,"[email protected]"
 
 ClientPlans: <----- this table
 1,1,6,2013-01-01,2013-01-03
 1,1,7,2013-01-03,2013-01-06
 1,1,6,2013-01-07,null
 
 
 
# Give me all the ids of clients which were ever on a given plan id. For example, plan id 1

 select distinct client_id from ClientPlans where plan_id = '1'
 
 Clients.where()

scope :for_a_plan 

ClientPlans.where(id: 1).map {|cp| cp.client.email }.uniq

# Give me the email addresses of clients ever on a given plan id

sum.rb

# Given an array of positive integers, give me all the pairs which sum to 100. No duplicates - [51, 49, 51] should only output one pair, 51-49.

# Example data:

# sample = [0, 1, 99, 100, 0, 10, 90, 30, 55, 33, 55, 75]

# output; 1,99,   10,90, 

def pairs(ints)
    res = []
    ints.each_with_index do |v, i|
        ints[i, ints.size].each do |s|
            if v + s == 100
               res << [v, s].sort
            end
        end
    end
    res = res.uniq
end

puts pairs([0, 1, 99, 100, 0, 10, 90, 30, 55, 33, 55, 75]).inspect

#[[0, 100], [1, 99], [10, 90]]