Trapping Rain Waterhard

#include <iostream>
#include <vector>
using namespace std;

int trap(vector<int>& height) {
    // TODO: two-pointer approach
    return 0;
}

int main() {
    vector<int> a = {0,1,0,2,1,0,1,3,2,1,2,1};
    vector<int> b = {4,2,0,3,2,5};
    cout << trap(a) << endl; // 6
    cout << trap(b) << endl; // 9
    return 0;
}