WORST_CASE(?,O(n^1))
* Step 1: Bounds WORST_CASE(?,O(n^1))
    + Considered Problem:
        - Strict TRS:
            @(dd(x,xs),ys) -> dd(x,@(xs,ys))
            @(nil(),xs) -> xs
            flatten(dd(x,xs)) -> @(x,flatten(xs))
            flatten(nil()) -> nil()
        - Signature:
            {@/2,flatten/1} / {dd/2,nil/0}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {@,flatten} and constructors {dd,nil}
    + Applied Processor:
        Bounds {initialAutomaton = minimal, enrichment = match}
    + Details:
        The problem is match-bounded by 1.
        The enriched problem is compatible with follwoing automaton.
          @_0(2,2) -> 1
          @_1(2,2) -> 3
          @_1(2,4) -> 1
          @_1(2,4) -> 4
          dd_0(2,2) -> 1
          dd_0(2,2) -> 2
          dd_0(2,2) -> 3
          dd_1(2,1) -> 1
          dd_1(2,3) -> 1
          dd_1(2,3) -> 3
          dd_1(2,4) -> 1
          dd_1(2,4) -> 4
          flatten_0(2) -> 1
          flatten_1(2) -> 1
          flatten_1(2) -> 4
          nil_0() -> 1
          nil_0() -> 2
          nil_0() -> 3
          nil_1() -> 1
          nil_1() -> 4
          2 -> 1
          2 -> 3
          4 -> 1
* Step 2: EmptyProcessor WORST_CASE(?,O(1))
    + Considered Problem:
        - Weak TRS:
            @(dd(x,xs),ys) -> dd(x,@(xs,ys))
            @(nil(),xs) -> xs
            flatten(dd(x,xs)) -> @(x,flatten(xs))
            flatten(nil()) -> nil()
        - Signature:
            {@/2,flatten/1} / {dd/2,nil/0}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {@,flatten} and constructors {dd,nil}
    + Applied Processor:
        EmptyProcessor
    + Details:
        The problem is already closed. The intended complexity is O(1).

WORST_CASE(?,O(n^1))