<p>In a gold mine <code>grid</code> of size <code>m x n</code>, each cell in this mine has an integer representing the amount of gold in that cell, <code>0</code> if it is empty.</p>

<p>Return the maximum amount of gold you can collect under the conditions:</p>

<ul>
	<li>Every time you are located in a cell you will collect all the gold in that cell.</li>
	<li>From your position, you can walk one step to the left, right, up, or down.</li>
	<li>You can&#39;t visit the same cell more than once.</li>
	<li>Never visit a cell with <code>0</code> gold.</li>
	<li>You can start and stop collecting gold from <strong>any </strong>position in the grid that has some gold.</li>
</ul>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> grid = [[0,6,0],[5,8,7],[0,9,0]]
<strong>Output:</strong> 24
<strong>Explanation:</strong>
[[0,6,0],
 [5,8,7],
 [0,9,0]]
Path to get the maximum gold, 9 -&gt; 8 -&gt; 7.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> grid = [[1,0,7],[2,0,6],[3,4,5],[0,3,0],[9,0,20]]
<strong>Output:</strong> 28
<strong>Explanation:</strong>
[[1,0,7],
 [2,0,6],
 [3,4,5],
 [0,3,0],
 [9,0,20]]
Path to get the maximum gold, 1 -&gt; 2 -&gt; 3 -&gt; 4 -&gt; 5 -&gt; 6 -&gt; 7.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>m == grid.length</code></li>
	<li><code>n == grid[i].length</code></li>
	<li><code>1 &lt;= m, n &lt;= 15</code></li>
	<li><code>0 &lt;= grid[i][j] &lt;= 100</code></li>
	<li>There are at most <strong>25 </strong>cells containing gold.</li>
</ul>

class Solution {
public:
    
  
    
 
    int solve(int i,int j,int n,int m,vector<vector<int>>& vis,vector<vector<int>>& mat){
         if (i < 0 || i >= n || j < 0 || j >= m || vis[i][j] || mat[i][j] == 0) {
        return 0;
    }
        int gold=mat[i][j];

        vis[i][j]=1;
       int u = solve(i + 1, j, n, m, vis, mat);
        int d = solve(i - 1, j, n, m, vis, mat);
        int l = solve(i, j - 1, n, m, vis, mat);
        int r = solve(i, j + 1, n, m, vis, mat);
        vis[i][j]=0;
       return gold + max({u,d,l,r});
        

    }
    int getMaximumGold(vector<vector<int>>& grid) {
        int n = grid.size();
        if (n == 0) return 0;
        int m = grid[0].size();
        if (m == 0) return 0;

        vector<vector<int>> vis(n, vector<int>(m, 0));
        int mm=0;
         for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                if (grid[i][j] != 0) {
                    mm = max(mm, solve(i, j, n, m, vis, grid));
                }
            }
        }
         return mm;

        
        

        
    }
};
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