Solution.cpp

class Solution {
public:
    int numDistinctIslands(vector<vector<int>>& grid) {
        unordered_set<string> paths;
        string path;
        int m = grid.size(), n = grid[0].size();
        int dirs[5] = {-1, 0, 1, 0, -1};

        function<void(int, int, int)> dfs = [&](int i, int j, int k) {
            grid[i][j] = 0;
            path += to_string(k);
            for (int h = 1; h < 5; ++h) {
                int x = i + dirs[h - 1], y = j + dirs[h];
                if (x >= 0 && x < m && y >= 0 && y < n && grid[x][y]) {
                    dfs(x, y, h);
                }
            }
            path += to_string(k);
        };

        for (int i = 0; i < m; ++i) {
            for (int j = 0; j < n; ++j) {
                if (grid[i][j]) {
                    dfs(i, j, 0);
                    paths.insert(path);
                    path.clear();
                }
            }
        }
        return paths.size();
    }
};