Given an array of strictly the characters 'R', 'G', and 'B', segregate the values of the array so that all the Rs come first, the Gs come second, and the Bs come last. You can only swap elements of the array. Do this in linear time and in-place. For example, given the array ['G', 'B', 'R', 'R', 'B', 'R', 'G'], it should become ['R', 'R', 'R', 'G…

daily-coding-problem-35.rb

#!/usr/bin/env ruby

def sort(array)
    order = ["R","G","B"]
    res = Array.new(order.size()) { Array.new }
    array.each { |c| res[order.index(c)] << c }
    return res.flatten
end 

def sort_proper(array)
    array.each_with_index do |e, i|
        next if i == 0
        swap(array, i)
    end 
    return array
end 

def compare(this, other) 
    order = ["R","G","B"]
    a = order.index(this)
    b = order.index(other)
    return b <=> a
end 

def swap(array, idx)
    valid = idx - 1 >= 0
    while idx - 1 >= 0 
        larger = compare(array[idx], array[idx-1]) == 1
        array[idx], array[idx-1] = array[idx-1], array[idx] if larger
        idx -= 1
    end 
    return array 
end

unsorted = ['G', 'B', 'R', 'R', 'B', 'R', 'G']
puts sort_proper(unsorted)