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: { sum(0()) -> 0() , sum(s(x)) -> +(sum(x), s(x)) , sum1(0()) -> 0() , sum1(s(x)) -> s(+(sum1(x), +(x, x))) } 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: { sum(0()) -> 0() , sum(s(x)) -> +(sum(x), s(x)) , sum1(0()) -> 0() , sum1(s(x)) -> s(+(sum1(x), +(x, x))) } 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(sum) = {}, safe(0) = {}, safe(s) = {1}, safe(+) = {1, 2}, safe(sum1) = {} and precedence empty . Following symbols are considered recursive: {sum, sum1} The recursion depth is 1. For your convenience, here are the satisfied ordering constraints: sum(0();) > 0() sum(s(; x);) > +(; sum(x;), s(; x)) sum1(0();) > 0() sum1(s(; x);) > s(; +(; sum1(x;), +(; x, x))) 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: { sum(0()) -> 0() , sum(s(x)) -> +(sum(x), s(x)) , sum1(0()) -> 0() , sum1(s(x)) -> s(+(sum1(x), +(x, x))) } Obligation: innermost runtime complexity Answer: YES(O(1),O(1)) Empty rules are trivially bounded Hurray, we answered YES(O(1),O(n^1))