Given an array of numbers, how can I select the number in the array that's has been repeated the most times?
arr = [4,3, 3, 2, 1, 3, 3, 3, 4, 4, 4, 4, 0, 0, 0, 1, 3, 4, 0]
1 Answer
Here it is for just repeated:
arr = [4,3, 3, 2, 1, 3, 3, 3, 4, 4, 4, 4, 0, 0, 0, 1, 3, 4, 0]
arr.group_by{|e| e}.max_by{|k,v| v.size}.first
# => 4
or
arr = [4,3, 3, 2, 1, 3, 3, 3, 4, 4, 4, 4, 0, 0, 0, 1, 3, 4, 0]
arr.uniq.max_by{|e| arr.count(e)}
# => 4
Another is for repeated consecutively :
arr = [4,3, 3, 2, 1, 3, 3, 3, 4, 4, 4, 4, 0, 0, 0, 1, 3, 4, 0]
arr.chunk{|e| e}.max_by{|e| e.last.size}.first
# => 4
As per the @Tessi Benchmark report :
require 'benchmark'
iterations = 10_000
arr = Array.new(1000) {(rand()*100).to_i}
def max_babai1(arr)
arr.group_by{|e| e}.max_by{|k,v| v.size}.first
end
def max_babai2(arr)
arr.uniq.max_by{|e| arr.count(e)}
end
Benchmark.bm do |bm|
bm.report('babai1') do
iterations.times do
max_babai1 arr
end
end
bm.report('babai2') do
iterations.times do
max_babai2 arr
end
end
end
Output
ruby --version
ruby 2.0.0p247 (2013-06-27 revision 41674) [x86_64-linux]
ruby bench.rb
user system total real
babai1 1.700000 0.000000 1.700000 ( 1.707292)
babai2 29.630000 0.010000 29.640000 ( 29.769966)
15 Comments
Nicholas Alek
That's the one!!! Thanks. Can you walk me through your code?
Arup Rakshit
@NicholasAlek which one is your one? First one(repeated) or last one(repeated consecutively) ? :)
Nicholas Alek
Ahhh, doesn't matter which order, first or last.
firien
for the
repeated one you can use chunk if you sort first: arr.sort.chunk{|v|v}.max_by{|val,a| a.size}.first. Although neither implementation handles ties.Arup Rakshit
@firien why sort is needed ? You probably didn't catch the difference between the 2 codes.
|
[1, 1, 2, 2, 2, 1, 1]2 or 1?