Which of these countries does not border Algeria?

Malawi is the country that does not border Algeria.

Malawi, officially the Republic of Malawi, is a landlocked country in southeastern Africa that was formerly known as Nyasaland. It is bordered by Zambia to the west, Tanzania to the north and northeast, and Mozambique surrounding on the east, south and southwest. Malawi spans over 118,484 km2 (45,747 sq mi) and has an estimated population of 18,143,217 (as of July 2018). Lake Malawi, also known as Lake Nyasa, takes up about a third of Malawi's area. Its capital is Lilongwe, which is also the country's largest city.

Algeria, officially the People's Democratic Republic of Algeria, is a country in the Maghreb region of North Africa. Algeria is bordered to the northeast by Tunisia, to the east by Libya, to the southeast by Niger, to the southwest by Mali, Mauritania, and the Western Saharan territory, to the west by Morocco, and to the north by the Mediterranean Sea.