Given an?m x n?binary matrix?mat, return?the distance of the nearest?0?for each cell.

The distance between two adjacent cells is?1.

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Example 1:

Input: mat = [[0,0,0],[0,1,0],[0,0,0]]

Output: [[0,0,0],[0,1,0],[0,0,0]]

Example 2:

Input: mat = [[0,0,0],[0,1,0],[1,1,1]]

Output: [[0,0,0],[0,1,0],[1,2,1]]

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Constraints:

• m == mat.length

• n == mat[i].length

• 1 <= m, n <= 104

• 1 <= m * n <= 104

• mat[i][j]?is either?0?or?1.

• There is at least one?0?in?mat.

BFS計(jì)算，算是經(jīng)典題目；得多練練這個(gè)。

Runtime:?13 ms, faster than?77.51%?of?Java?online submissions for?01 Matrix.

Memory Usage:?44.3 MB, less than?92.71%?of?Java?online submissions for?01 Matrix.