The official currency in Algeria is the Algerian Dinar.
Its value fluctuates, so the exchange rate against the euro is not fixed. Roughly speaking, the value is about €1 = 155DZD (May 2022).
There are exchange offices at the airport in Algiers, but we advise against changing money on the black market as it is not legal and punishable by imprisonment.
In all major cities there are ATMs where you can withdraw local currency by Visa card, but we always recommend cash for convenience and personal safety.
Euros are not refused for some souvenir deals in southern towns where they are used to tourist passage.
The local currency is not exportable, so it will have to be spent in full before leaving.