I think one of the coastal cities, maybe Oran, had close to an European majority and I never knew why they didn't try the strategy of holding on to that and giving the rest of the country independence.
The FLN likely would not have accepted that, and it would have become a very costly thing to maintain. It could have been done, though, I believe. Part of the issue was that France's claim in the conflict was that French Algeria was an integral part of France, being a department, and that agreeing to some kind of territorial partitioning would have made such a claim entirely hollow. Another part of the issue was that, as in other areas dealing with similar issues at the time, like in Kenya or Northern Rhodesia, the government in the mother country really started to nurture a strong dislike for the local settler population and its resistance towards government initiatives meant to head off further conflict.
France would have been better off in this scenario if, like Spain did with Ceuta, Ifni, and Melilla, it had made the decision to administratively consider Oran and Algiers to be French Departments and the rest of Algeria to be a protectorate, that way, it was not stuck in an all or nothing proposition. That way, it could have had something to bargain.