Using Ruby, sort each coach by consecutive season tenures. Some seasons have two coaches which implies that the coach was fired/removed mid-season. The result should be something like [[name, start_season, end_season], [name, start_season, end_season]] where the order is by ascending start_season.

coaches.csv

How does this look

{:name=>"Bill Musselman", :startyear=>1989, :endyear=>1991}
{:name=>"Jimmy Rodgers", :startyear=>1991, :endyear=>1993}
{:name=>"Sidney Lowe", :startyear=>1992, :endyear=>1994}
{:name=>"Bill Blair", :startyear=>1994, :endyear=>1996}
{:name=>"Flip Saunders", :startyear=>1995, :endyear=>1900}
{:name=>"Flip Saunders", :startyear=>2000, :endyear=>2005}
{:name=>"Kevin McHale", :startyear=>2004, :endyear=>2005}
{:name=>"Dwane Casey", :startyear=>2005, :endyear=>2007}
{:name=>"Randy Wittman", :startyear=>2006, :endyear=>2009}
{:name=>"Kevin McHale", :startyear=>2008, :endyear=>2009}
{:name=>"Kurt Rambis", :startyear=>2009, :endyear=>2011}
{:name=>"Rick Adelman", :startyear=>2011, :endyear=>2014}
{:name=>"Flip Saunders", :startyear=>2014, :endyear=>2015}
{:name=>"Sam Mitchell", :startyear=>2015, :endyear=>2016}

require 'csv'

coaches = CSV.read('coaches.csv', {headers: true}).map do |row| 
  startyear, endyear = row[0].split('-')
  {name: row[1], 
   startyear: startyear.to_i , 
   endyear: "#{startyear.to_s[0,2]}#{endyear}".to_i} 
end

def merged(record)
  record.sort_by{|season| season[:startyear]}.reduce([]) do |memo, season|
    if memo.size == 0
      memo << season
    else
      if memo.last[:endyear] == season[:startyear]
        memo.last[:endyear] = season[:endyear]
      else
        memo << season
      end
    end
    memo
  end
end

puts coaches.group_by{|c| c[:name]}
       .map{|name, record| merged(record)}.flatten

there's a Y2K problem with Flip Sanders :)