01 Matrix

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