从方法（Java）删除尾递归

Question

I have this method:

    private String computePerm(int iteration) {
        if (iteration < n + 1) {
            return Character.toString((char) (iteration + 48));
        } else {
            if (iteration % n == 0) {
                return computePerm((iteration / n) - 1) + computePerm(((iteration - 1) % n + 1));
            } else {
                return computePerm(iteration / n) + computePerm(iteration % n);
            }
        }
   }

It computes a permutation induced by a single breadth-first search traversal. I'm using it to solve Post's correspondence problem . However, I suspect it is tail-recursive, and it seems to incur an ugly overhead on some instances of the problem.

How can I remove tail-recursion while preserving the method's behavior?

Answer 1

This does what you're after (the permutation of an alphabet of size n ):

private static String computePerm(int iteration) {
    return Integer.toString(iteration, n);
}