<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 dx[4] = {-1,0,0,1};
    int dy[4] = {0,-1,1,0};
    void f(vector<vector<int>> &grid,int srcRow,int srcCol,int currGold,int &maxGold,vector<vector<bool>> &visited)
    {
        visited[srcRow][srcCol]=1;
        currGold+=grid[srcRow][srcCol];
        maxGold = max(maxGold,currGold);
        for(int i=0;i<4;i++)
        {
            int destRow = srcRow + dx[i];
            int destCol = srcCol + dy[i];
            if(destRow>=0 && destRow<grid.size() && destCol>=0 && destCol<grid[0].size() && grid[destRow][destCol]!=0 && visited[destRow][destCol]==0)
            {
                f(grid,destRow,destCol,currGold,maxGold,visited);
            }
        }
        visited[srcRow][srcCol]=0;
        currGold-=grid[srcRow][srcCol];
    }
    int getMaximumGold(vector<vector<int>>& grid)
    {
        int m = grid.size();
        int n = grid[0].size();
        int maxGold=0;
        for(int i=0;i<m;i++)
        {
            for(int j=0;j<n;j++)
            {
                vector<vector<bool>> visited(m,vector<bool>(n,false));
                if(grid[i][j]!=0) 
                {
                    f(grid,i,j,0,maxGold,visited);
                }
            }
        }
        return maxGold;
    }
};
13800