决策树：

代码设计

代码：

class Solution {boolean[][] vis;int ret,m,n;public int getMaximumGold(int[][] grid) {m = grid.length;n = grid[0].length;vis = new boolean[m][n]; for(int i = 0; i < m; i++)for(int j = 0; j < n; j++){//剪枝if (grid[i][j] != 0 && !vis[i][j]){vis[i][j] = true;dfs(grid,i,j,grid[i][j]);vis[i][j] = false;//回溯}}return ret;    }int[] dx = {-1,1,0,0};int[] dy = {0,0,-1,1};//这里局部变量会自己恢复现场private void dfs(int[][] grid, int i, int j, int path){ret = Math.max(ret,path);for(int k = 0; k < 4; k++){int x = i + dx[k];int y = j + dy[k];//剪枝if(x >= 0 && x < m && y >= 0 && y < n && !vis[x][y] && grid[x][y] != 0){vis[x][y] = true;dfs(grid,x,y,path + grid[x][y]);vis[x][y] = false;//回溯}}}
}