quicksort.rb

#sorah's quicksort

def get_center(ar);if ar.length % 2 != 0;ar[(ar.length) / 2];else;ar[(ar.length-1) / 2];end;end
def get_center_index(ar);if ar.length % 2 != 0;return (ar.length) / 2;else;return (ar.length-1) / 2;end;end
def wsort
  zen_pi = get_center_index(zen)
  zen_p = get_center(zen)
  i = nil
  flag = false
    zen.each_index {|n|
      if zen_p <= zen[n]
        i = n
        break
      end
    }
    zen.reverse.each {|n|
      if zen_p >= n
        j = zen.index(n)
        break
      end
    }
    if i < j
      tmpi = zen[i]
      tmpj = zen[j]
      zen[i] = tmpj
      zen[j] = tmpi
      flag = true
    else
      flag = false
    end
  while flag
    flag = false
    zen[i+1 .. (zen.length-1)].each {|n|
      if zen_p <= n
        i = zen.index(n)
        break
      end
    }
    zen[0 .. j-1].reverse.each {|n|
      if zen_p >= n
        j = zen.index(n)
        break
      end
    }
    if i < j
      tmpi = zen[i]
      tmpj = zen[j]
      zen[i] = tmpj
      zen[j] = tmpi
      flag = true
    else
      flag = false
    end
  end
  return [zen,i,j]
end
def quicksort ar
  #0 1 [2] 3 4
  #[0..2-1] [2+1..(ar.length-1)]
  #pipot = get_center(ar)
  pivot = get_center_index(ar)
  zen = ar[0 .. pivot-1]
  ato = ar[pivot+1 .. (ar.length-1)]
  #前半処理
  flag = true
  sort1 = wsort(zen)
  while flag
    wsort sort1[0][0..(sort1[1]-1)]
  end
end