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01 Matrix

MediumP2Coding

Given a binary matrix mat, return a matrix of the same size where each cell holds the distance to the nearest 0. Distance is the number of up, down, left or right steps between two cells. The matrix contains at least one 0.

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]]

Constraints

  • 1 <= rows, cols <= 10^4 with rows * cols <= 10^4
  • mat[i][j] is 0 or 1
  • At least one 0 exists.

Hints

Run checks the 3 visible tests, Submit all 9.