黄金矿工

/*
 * 使用Java Stream解决这个问题并不直接，因为Stream主要用于处理集合和数组的并行计算。
 * 这里我们依旧使用DFS，但采用Java 8中的Optional等特性来优化代码。
 */

import java.util.Optional;

public class GoldMineStream {
    private static final int[] directions = {0, 1, 0, -1, 0};
    private int maxGold = 0;
    
    public int getMaximumGold(int[][] grid) {
        int m = grid.length, n = grid[0].length;
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (grid[i][j] > 0) {
                    dfs(grid, i, j, 0);
                }
            }
        }
        return maxGold;
    }
    
    private void dfs(int[][] grid, int x, int y, int currentGold) {
        currentGold += grid[x][y];
        maxGold = Math.max(maxGold, currentGold);
        int original = grid[x][y];
        grid[x][y] = 0;
        Optional.of(directions).stream().flatMap(dir -> {
            int nx = x + dir[0];
            int ny = y + dir[1];
            if (nx >= 0 && nx < grid.length && ny >= 0 && ny < grid[0].length && grid[nx][ny] > 0) {
                dfs(grid, nx, ny, currentGold);
            }
            return Optional.empty().stream();
        });
        grid[x][y] = original;
    }
}