class Solution {
    public int trap(int[] height) {
        if (height.length < 2) return 0;

        int totalWater = 0;

        int max1 = height[0];
        int max2 = 0;
        int sum1 = 0;
        int sum2 = 0;
        int n1 = 0;
        int n2 = 0;
        for (int i = 1; i < height.length; i++) {
            int h = height[i];
            if (h > max1) {
                max2 = max1;
                System.out.println("i=" + i + " max1=" + max1 + " max2=" + max2  + " n1=" + n1 + " n2="+ n2 + " sum1=" + sum1 + " sum2=" + sum2 + " delta " + ((n1+n2)*max2 - sum1 - sum2));
                totalWater += ((n1 + n2)*max2 - sum1 - sum2;
                max1 = h;
                max2 = 0;
                sum1 = 0;
                sum2 = 0;
                n1 = 0;
                n2 = 0;
            }
            else {
                n2++;
                sum2 += h;
                if (h >= max2){
                    max2 = h;
                    sum1 += sum2;
                    sum2 = 0;
                    n1 += n2;
                }
            }
        }

System.out.println(" max1=" + max1 + " max2=" + max2  + " n1=" + n1 + " sum1=" + sum1 + " sum2=" + sum2 + " delta " + (n1*max2 - sum1));

        totalWater += n1*max2 - sum1;

        return totalWater;
    }