1219. Path with Maximum Gold

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

Return the maximum amount of gold you can collect under the conditions:

• Every time you are located in a cell you will collect all the gold in that cell.
• From your position, you can walk one step to the left, right, up, or down.
  You can’t visit the same cell more than once.
• Never visit a cell with 0 gold.
• You can start and stop collecting gold from any position in the grid that has some gold.

class Solution {
    int dfs(vector<vector<int>>& grid, int y, int x) {
        if(0 > y or 0 > x or y >= grid.size() or x >= grid[y].size() or grid[y][x] == 0)
            return 0;
        int cell = grid[y][x];
        grid[y][x] = 0;
        int res = cell;
        res = max(res, dfs(grid,y+1,x) + cell);
        res = max(res, dfs(grid,y-1,x) + cell);
        res = max(res, dfs(grid,y,x+1) + cell);
        res = max(res, dfs(grid,y,x-1) + cell);
        grid[y][x] = cell;
        return res;
    }
public:
    int getMaximumGold(vector<vector<int>>& grid) {
        int res = 0;
        for(int i = 0; i < grid.size(); i++) {
            for(int j = 0; j < grid[i].size(); j++)
                res = max(res, dfs(grid,i,j));
        }
        return res;
    }
};