trapping rainwater

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int trap(vector<int>& height) {
    if (height.empty()) return 0;

    int n = height.size();
    vector<int> left_max(n);
    vector<int> right_max(n);
    
    // Fill left_max
    left_max[0] = height[0];
    for (int i = 1; i < n; ++i) {
        left_max[i] = max(left_max[i - 1], height[i]);
    }

    // Fill right_max
    right_max[n - 1] = height[n - 1];
    for (int i = n - 2; i >= 0; --i) {
        right_max[i] = max(right_max[i + 1], height[i]);
    }

    // Calculate trapped water
    int trapped_water = 0;
    for (int i = 0; i < n; ++i) {
        trapped_water += min(left_max[i], right_max[i]) - height[i];
    }

    return trapped_water;
}

int main() {
    vector<int> height = {0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1};
    int result = trap(height);
    cout << "Trapped rainwater: " << result << " units" << endl;
    return 0;
}