SDE - Intern

You have been given a grid containing some oranges. Each cell of this grid has one of the three integers values:

Value 0 - representing an empty cell.

Value 1 - representing a fresh orange.

Value 2 - representing a rotten orange.

Every second, any fresh orange that is adjacent(4-directionally) to a rotten orange becomes rotten.

Your task is to find out the minimum time after which no cell has a fresh orange. If it's impossible to rot all the fresh oranges then print -1.

Note:

1. The grid has 0-based indexing.
2. A rotten orange can affect the adjacent oranges 4 directionally i.e. Up, Down, Left, Right.

You are given an integer ‘N’. You need to find an array of size 2*N that satisfies the following two conditions.

1. All numbers from 1 to N should appear exactly twice in the array.

2. The distance between the second occurrence and the first occurrence of any number should exactly be equal to the value of that number.

The distance between two numbers at indices ‘i’ and ‘j’ is defined as (j-i-1) where i < j.

If no such array exists, then you should return an empty array.

For example :

For N = 3 one valid array is [3,1,2,1,3,2].