Problems are solved with algorithms. Algorithms are either efficient or not efficient. Algorithms that are efficient can be solved in polynomial time (i.e. time

Problems are solved with algorithms. Algorithms are either efficient or not efficient. Algorithms that are efficient can be solved in polynomial time (i.e. time can be estimated with Big Oh notation). So they have a deterministic algorithm. For NP problems, you only have a brute force solution that is inefficient. https://simple.wikipedia.org/wiki/P_versus_NP https://simple.wikipedia.org/wiki/P_versus_NP