Kata

Given an array of integers of any length, return an array that has 1 added to the value represented by the array.

If the array is invalid (empty, or contains negative integers or integers with more than 1 digit), return nil (or your language's equivalent).

Examples

Valid arrays

• [4, 3, 2, 5] would return [4, 3, 2, 6] (4325 + 1 = 4326)
• [1, 2, 3, 9] would return [1, 2, 4, 0] (1239 + 1 = 1240)
• [9, 9, 9, 9] would return [1, 0, 0, 0, 0] (9999 + 1 = 10000)
• [0, 1, 3, 7] would return [0, 1, 3, 8] (0137 + 1 = 0138)

Invalid arrays

• [] is invalid because it is empty
• [1, -9] is invalid because -9 is not a non-negative integer
• [1, 2, 33] is invalid because 33 is not a single-digit integer