int trap(vector<int>& height) {

int n = height.size();

int volum = 0;

stack<int> s;

for (int i = 0; i < n; ++i) {

while (!s.empty() && height[i] > height[s.top()]) {

int b_h = height[s.top()];

s.pop();

if (s.empty())

break;

int left = s.top();

int t_width = i - left - 1;

int t_height = min(height[i], height[left]) - b_h;

volum += t_width * t_height;

}

s.push(i);

}

return volum;

}

Solution sol;

vector<int> height = { 0,1,0,2,1,0,1,3,2,1,2,1 };

int res = sol.trap(height);

cout << "res is " << res << endl;

return (0);