class Solution {
private:
    int calculateArea(int left, int right, vector<int>& height){
        return (right - left) * min(height[left], height[right]);
    }

public:
    int trap(vector<int>& height) {
        int totalArea = 0;

        if(height.size() <= 2)
            return 0;

        int left = 0, right = 0;

        while(height[left] == 0){
            ++left;

            if(left == height.size()-2)
                break;
        }
        right = left+2;

        while(left < right && right <= height.size()-1){
            totalArea += calculateArea(left, right, height);

            left = right;
            right = left+2;
        }

        return totalArea;
    }
};