rewrite [getElem_append_left as bs hj']
α : Type u
as bs : Array α
has : Nodup as
hbs : Nodup bs
hdisj : ∀ (i j : Nat) (hi : i < size as) (hj : j < size bs), as[i] ≠ bs[j]
i j : Nat
hi : i < size (as ++ bs)
hj : j < size (as ++ bs)
hi' : i < size as
hj' : j < size as
⊢ as[i] = (as ++ bs)[j] → i = j
α : Type u
as bs : Array α
has : Nodup as
hbs : Nodup bs
hdisj : ∀ (i j : Nat) (hi : i < size as) (hj : j < size bs), as[i] ≠ bs[j]
i j : Nat
hi : i < size (as ++ bs)
hj : j < size (as ++ bs)
hi' : i < size as
hj' : j < size as
⊢ as[i] = as[j] → i = j