てきとうだった

gistfile1.rb

#!/usr/bin/ruby

def qsort(first,last,ary)

    if first >= last
        return
    end

    target = ary[first]
    buf1 = Array.new
    buf2 = Array.new

    for i in first+1..last
       if ary[i] < target
           buf1.push ary[i]
       else
           buf2.push ary[i]
       end
    end

    ary[first..last] = buf1 + [target] + buf2

    qsort(first, first+buf1.length-1, ary)
    qsort(last-buf2.length+1, last, ary)
end

sary = Array.new
N = 10
N.times do |i|
    sary[i] = rand(N)
end

p sary

qsort(0, N-1, sary)

p sary