$O(nm×lognm)$

class Solution {
public:
    int n, m;
    vector<vector<int>> g;
    int dx[8] = {-1, -1, 0, 1, 1, 1, 0, -1}, dy[8] = {0, 1, 1, 1, 0, -1, -1, -1};

    vector<int> pondSizes(vector<vector<int>>& land) {
        g = land;
        n = land.size(), m = land[0].size();

        vector<int> res;
        for (int i = 0; i < n; i ++ ) {
            for (int j = 0; j < m; j ++ ) {
                if (g[i][j] == 0) {
                    int cnt = dfs(i, j);
                    res.push_back(cnt);
                }
            }
        }

        sort(res.begin(), res.end());

        return res;
    }

    int dfs(int x, int y) {
        int cnt = 1;
        g[x][y] = 1;

        for (int i = 0; i < 8; i ++ ) {
            int a = x + dx[i], b = y + dy[i];
            if (a >= 0 && a < n && b >= 0 && b < m && g[a][b] == 0)
                cnt += dfs(a, b);
        }

        return cnt;
    }
};