This will work for lists of length 4
or greater:
correct( [H1|[H2|T1]], X, [H1|[X|T2]] ) :-
reverse(T1, [HR|[X|TR]]),
reverse([HR|[H2|TR]], T2).
| ?- correct( [1,2,3,4,5,6], X, L ).
L = [1,5,3,4,2,6]
X = 5
(1 ms) yes
| ?-
You can include the shorter cases, if that's the intention, by adding two more predicates, bringing the solution to:
correct( [A,X], X, [X,A] ).
correct( [A,X,B], X, [A,X,B] ).
correct( [H1|[H2|T1]], X, [H1|[X|T2]] ) :-
reverse(T1, [HR|[X|TR]]),
reverse([HR|[H2|TR]], T2).