f=->a{c=Hash.new 0
r=[[]]
a.map{|e|2==(c[e]+=1)?r<<[]:r[-1]<<e}
r}
input = [2, 1, 1, 2, 3, 2, 2, 4, 5, 6, 7, 3, 7, 0, 5]
p f[input]
Zj0tPmF7Yz1IYXNoLm5ldyAwCnI9W1tdXQphLm1hcHt8ZXwyPT0oY1tlXSs9MSk/cjw8W106clstMV08PGV9CnJ9CgppbnB1dCA9IFsyLCAxLCAxLCAyLCAzLCAyLCAyLCA0LCA1LCA2LCA3LCAzLCA3LCAwLCA1XQoKcCBmW2lucHV0XQ==
[[2, 1], [], [3, 2, 2, 4, 5, 6, 7], [], [0], []]