Explanation

Given a grid of dimension nxm where each cell in the grid can have values 0, 1 or 2 which has the following meaning: 0 : Empty cell 1 : Cells have fresh oranges 2 : Cells have rotten oranges We have to determine what is the earliest time after which all the oranges are rotten. A rotten orange at index [i,j] can rot other fresh orange at indexes [i-1,j], [i+1,j], [i,j-1], [i,j+1] (up, down, left and right) in unit time. Example 1: Input: grid = {{0,1,2},{0,1,2},{2,1,1}} Output: 1 Explanation: The grid is- 0 1 2 0 1 2 2 1 1 Oranges at positions (0,2), (1,2), (2,0) will rot oranges at (0,1), (1,1), (2,2) and (2,1) in unit time. Example 2: Input: grid = {{2,2,0,1}} Output: -1 Explanation: The grid is- 2 2 0 1 Oranges at (0,0) and (0,1) can't rot orange at (0,3).