<p>You are given an <code>m x n</code> <code>grid</code> where each cell can have one of three values:</p>

<ul>
	<li><code>0</code> representing an empty cell,</li>
	<li><code>1</code> representing a fresh orange, or</li>
	<li><code>2</code> representing a rotten orange.</li>
</ul>

<p>Every minute, any fresh orange that is <strong>4-directionally adjacent</strong> to a rotten orange becomes rotten.</p>

<p>Return <em>the minimum number of minutes that must elapse until no cell has a fresh orange</em>. If <em>this is impossible, return</em> <code>-1</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2019/02/16/oranges.png" style="width: 650px; height: 137px;" />
<pre>
<strong>Input:</strong> grid = [[2,1,1],[1,1,0],[0,1,1]]
<strong>Output:</strong> 4
</pre>

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

<pre>
<strong>Input:</strong> grid = [[2,1,1],[0,1,1],[1,0,1]]
<strong>Output:</strong> -1
<strong>Explanation:</strong> The orange in the bottom left corner (row 2, column 0) is never rotten, because rotting only happens 4-directionally.
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> grid = [[0,2]]
<strong>Output:</strong> 0
<strong>Explanation:</strong> Since there are already no fresh oranges at minute 0, the answer is just 0.
</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;= 10</code></li>
	<li><code>grid[i][j]</code> is <code>0</code>, <code>1</code>, or <code>2</code>.</li>
</ul>

class Solution:
    def orangesRotting(self, grid: List[List[int]]) -> int:

        '''
        grid = [[2,2,2],
                [2,2,0],
                [0,2,2]]

                t = 4
                fresh =6

        grid = [[2,2,2],
                [0,2,2],
                [1,0,2]]
                

        '''

        q = collections.deque()

        fresh = 0

        rows = len(grid)
        cols = len(grid[0])

        for r in range(rows):
            for c in range(cols):
                if grid[r][c] == 1:
                    fresh += 1
                if grid[r][c] == 2:
                    q.append((r,c))


        time = 0
        visit = set()
        directions = [(-1,0),(1,0),(0,-1),(0,1)]

        while q and fresh > 0:
            for i in range(len(q)):
                r,c = q.popleft()

                for dir in directions:
                    newR = r + dir[0]
                    newC = c + dir[1]

                    if newR < 0 or newC < 0 or newR >= rows or newC >= cols or (newR,newC) in visit or grid[newR][newC] != 1:
                        continue
                    grid[newR][newC] = 2
                    fresh -= 1
                    q.append((newR,newC))
                    visit.add((newR,newC))
            time += 1


        return time if fresh == 0 else -1

        
        
16500