public class Main {

    private int pitStart = -1, pitCenter = -1, pitFinish = -1;

    public static void main(String[] args) {
        int[] a = {0, 1, 3, -2, 0, 1, 0, -3, 2, 3};
        System.out.println("Result: " + new Main().solution(a));
    }

    private void startPit( int index){
        pitStart = index;
        System.out.printf("pit start: %s\n", pitStart);
    }

    private int finishPit( int[] a, int i){
        pitFinish = i;
        System.out.printf("pit start: %s, pit centre: %s, pit finish: %s\n", pitStart, pitCenter, pitFinish);

        int d =  Math.min( a[pitStart] - a[pitCenter], a[pitFinish] -  a[pitCenter]);
        clearPit();
        return d;
    }

    public int solution(int[] a) {
        int depth = -1;

        for (int i = 0; i < a.length - 1; i++) {

            if (a[i] >= a[i + 1] && isRising()) {
                depth = Math.max(depth, finishPit(a, i));
            }

            if (a[i] > a[i + 1] && pitStart < 0) {
                startPit(i);
            }

            if (a[i] < a[i + 1] && isDescending()) {
                centerPit(i);
            }

            if (a[i] == a[i + 1]) {
                clearPit();
            }
        }

        if (isRising()) {
            depth = Math.max(depth, finishPit(a, a.length - 1));
        }
        return depth;
    }

    private boolean isDescending() {
        return pitCenter < 0 && pitStart >= 0;
    }

    private boolean isRising() {
        return pitStart >= 0 && pitCenter >= 0;
    }

    private void clearPit() {
        pitStart = pitCenter = pitFinish = -1;
    }

    private void centerPit(int i) {
        pitCenter = i;
        System.out.printf("pit centre: %s\n", pitCenter);
    }
}