Here's how I think that the book should have ended:
The day after Piggy's death and Ralph is chased all over the island, he evades all the other savages with ease.
The other boys run way to the other end of the island, so it would be some time before they found him.
Ralph encounters the Navy officer and tells him that it's only him on the island. There's no one else except him. There were two more, but they died.
Ralph is put aboard the boat. The boat sails off towards the silver cruiser
The savages are abandoned on the island and we are left wondering their fates.
Is that how it should have ended?
Would it be realistic enough?