Agfdhyk

public final boolean isValidSolution(List<T> solution) throws NullPointerException {

    int inversions = 0;

    for (int i = 0; i < solution.size(); i++) {

        if (solution.get(i) == 0) {

            continue;

        }

        for (int j = i; j < solution.size(); j++) {

            if (solution.get(j) == 0) {

                continue;

            }

            if (solution.get(j) < solution.get(i)) {

                inversions++;

            }

        }

    }



    return (inversions & 1) == 0;

}

/**

* Checks that a solution is valid.

* 

* A valid solution consists of a list of states. The list should start with

* the initial state of the underlying problem. Then, it should have one or

* more additional states. Each state should be a successor of its

* predecessor. The last state should be a goal state of the underlying

* problem.

* 

* @param solution

* @return true iff this solution is a valid solution

* @throws NullPointerException

*         if solution is null

*/

Now I know that the code is wrong, the solution.get(i) is incompatible for type T and int. Please help me in this method.