YES(?,O(n^1)) We are left with following problem, upon which TcT provides the certificate YES(?,O(n^1)). Strict Trs: { from(X) -> cons(X, n__from(n__s(X))) , from(X) -> n__from(X) , sel(0(), cons(X, Y)) -> X , sel(s(X), cons(Y, Z)) -> sel(X, activate(Z)) , s(X) -> n__s(X) , activate(X) -> X , activate(n__from(X)) -> from(activate(X)) , activate(n__s(X)) -> s(activate(X)) } Obligation: innermost runtime complexity Answer: YES(?,O(n^1)) Arguments of following rules are not normal-forms: { sel(s(X), cons(Y, Z)) -> sel(X, activate(Z)) } All above mentioned rules can be savely removed. We are left with following problem, upon which TcT provides the certificate YES(?,O(n^1)). Strict Trs: { from(X) -> cons(X, n__from(n__s(X))) , from(X) -> n__from(X) , sel(0(), cons(X, Y)) -> X , s(X) -> n__s(X) , activate(X) -> X , activate(n__from(X)) -> from(activate(X)) , activate(n__s(X)) -> s(activate(X)) } Obligation: innermost runtime complexity Answer: YES(?,O(n^1)) The input was oriented with the instance of 'Small Polynomial Path Order (PS,1-bounded)' as induced by the safe mapping safe(from) = {1}, safe(cons) = {1, 2}, safe(n__from) = {1}, safe(n__s) = {1}, safe(sel) = {}, safe(0) = {}, safe(s) = {1}, safe(activate) = {} and precedence sel > from, sel > s, activate > from, activate > s, from ~ s, sel ~ activate . Following symbols are considered recursive: {activate} The recursion depth is 1. For your convenience, here are the satisfied ordering constraints: from(; X) > cons(; X, n__from(; n__s(; X))) from(; X) > n__from(; X) sel(0(), cons(; X, Y);) > X s(; X) > n__s(; X) activate(X;) > X activate(n__from(; X);) > from(; activate(X;)) activate(n__s(; X);) > s(; activate(X;)) Hurray, we answered YES(?,O(n^1))