01 Matrix

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. Cells are adjacent in the four cardinal directions.

Examples

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

• m == mat.length
• n == mat[i].length
• 1 <= m, n <= 10^4
• 1 <= m * n <= 10^4
• mat[i][j] is either 0 or 1.
• There is at least one 0 in mat.