You can always re-solve a problem, if you want that challenge. The fact that someone else has solved it shouldn't stop you, if your goal is to have a challenge.
Consider the difference between math and engineering (at the undergrad level). Math majors learn to solve solved problems, since the solutions are instructive; that is, they could accept a solution as truth but proving it is true has a greater value. However, engineers need to accept a lot of mathematical truths since the occupation applies these truths.
Either way, both of these systems are instructive. You should be able to reverse a process and discover its discrete parts, if that's your goal.
