48th day

#include <bits/stdc++.h>
using namespace std;
class Solution
{
public:
    long long trappingWater(int arr[], int n)
    {
        int left[n], right[n];
        left[0] = arr[0];
        right[n - 1] = arr[n - 1];
        for (int i = 1; i < n; i++)
        {
            left[i] = max(arr[i], left[i - 1]);
        }
        for (int i = n - 2; i >= 0; i--)
        {
            right[i] = max(arr[i], right[i + 1]);
        }
        long long ans = 0;
        for (int i = 0; i < n; i++)
        {
            ans += min(left[i], right[i]) - arr[i];
        }
        return ans;
    }
};
int main()
{
    int t;
    cin >> t;
    while (t--)
    {
        int n;
        cin >> n;

        int a[n];
        for (int i = 0; i < n; i++)
        {
            cin >> a[i];
        }
        Solution obj;
        cout << obj.trappingWater(a, n) << endl;
    }
    return 0;
}