Trapping Rain Waterhard

public class Main {
    public static int trap(int[] height) {
        // TODO: two-pointer approach
        return 0;
    }

    public static void main(String[] args) {
        System.out.println(trap(new int[]{0,1,0,2,1,0,1,3,2,1,2,1})); // 6
        System.out.println(trap(new int[]{4,2,0,3,2,5}));               // 9
    }
}