YES(O(1),O(n^1)) We are left with following problem, upon which TcT provides the certificate YES(O(1),O(n^1)). Strict Trs: { app(nil(), xs) -> nil() , app(cons(x, xs), ys) -> cons(x, app(xs, ys)) } Obligation: innermost runtime complexity Answer: YES(O(1),O(n^1)) We use the processor 'Small Polynomial Path Order (PS,1-bounded)' to orient following rules strictly. Trs: { app(nil(), xs) -> nil() , app(cons(x, xs), ys) -> cons(x, app(xs, ys)) } The induced complexity on above rules (modulo remaining rules) is YES(?,O(n^1)) . These rules are moved into the corresponding weak component(s). Sub-proof: ---------- The input was oriented with the instance of 'Small Polynomial Path Order (PS,1-bounded)' as induced by the safe mapping safe(app) = {}, safe(nil) = {}, safe(cons) = {1, 2} and precedence empty . Following symbols are considered recursive: {app} The recursion depth is 1. For your convenience, here are the satisfied ordering constraints: app(nil(), xs;) > nil() app(cons(; x, xs), ys;) > cons(; x, app(xs, ys;)) We return to the main proof. We are left with following problem, upon which TcT provides the certificate YES(O(1),O(1)). Weak Trs: { app(nil(), xs) -> nil() , app(cons(x, xs), ys) -> cons(x, app(xs, ys)) } Obligation: innermost runtime complexity Answer: YES(O(1),O(1)) Empty rules are trivially bounded Hurray, we answered YES(O(1),O(n^1))