Solution: Rotting Oranges

Problem Statement

Given a grid of empty cells, fresh oranges and rotten oranges, where rot spreads one step each minute to the four squares directly up, down, left and right of it, return the number of minutes until no fresh orange is left, or -1 if that never happens.

Examples

Example 1

• Input: grid = [[2,1,1],[1,1,0],[0,1,1]]
• Expected Output: 4

Example 2

• Input: grid = [[2,1,1],[0,1,1],[1,0,1]]
• Expected Output: -1

Example 3

• Input: grid = [[0,2]]
• Expected Output: 0