Erlang在列表中查找连续的相同元素

Question

I need to find consecutive same element from a LIST.

start from any position

ie [BCCDAB] expected result [cc] [BCDCBA] expected result []

any suggestion? thanks

Answer 1

extractcc(L) -> extractcc(L,[]).

etractcc([],R) -> lists:reverse(R);
extractcc([H,H|T],R) -> extactcc(T,[H,H|R]);
extractcc([_H|T],R) -> extractcc(T,R).

this will work for your example, but will have a strange behaviour if there are more than 2 consecutive elements. Here an example written in the shell:

1> Ex = fun Ex([],R) -> lists:reverse(R);
1> Ex([H,H|T],R) -> Ex(T,[H,H|R]);       
1> Ex([_H|T],R) -> Ex(T,R) end.          
#Fun<erl_eval.36.90072148>
2> E = fun(L) -> Ex(L,[]) end.
#Fun<erl_eval.6.90072148>
3> E([1,2,3,3,4,3]).
[3,3]
4> E([1,2,1,2,1]).
[]
5> E([1,2,2,2,3]).
[2,2]
6> E([1,2,2,2,2,3]).
[2,2,2,2]

I let you find how to code the expected behaviour.