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Intuition

The problem involves adding 1 to a number represented as an array of digits. My first thought was to convert the list of digits into an integer, perform the addition, and then split the resulting number back into its digits. Using Python's map and string manipulation makes this process straightforward and concise.

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Approach

1. Convert Digits to String:

   • Use map(str, digits) to convert each digit in the list to a string.

   • Use ''.join(...) to combine the strings into a single number as a string.

2. Convert String to Integer and Add One:

   • Use int(...) to convert the string to an integer.

   • Add 1 to the integer.

3. Convert the Result Back to Digits:

   • Convert the result back to a string with str(...).

   • Use map(int, ...) to convert each character back to an integer.

   • Use list(...) to collect the integers into a list.

This approach avoids complex looping or carry-over logic, leveraging Python's powerful built-in functions.

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Complexity

• Time complexity:
  $$O(n)$$
  The operations map, join, and list each traverse the digits list or the resulting string once, making the overall complexity linear with respect to the number of digits.

• Space complexity:
  $$O(n)$$
  Additional space is used to store intermediate strings and the final list of digits.

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Code

class Solution(object):
    def plusOne(self, digits):
        return list(map(int, str(int(''.join(map(str, digits))) + 1)))

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Example Test Cases

1. Input: [1, 2, 3]
   Output: [1, 2, 4]
   Explanation: The number 123 becomes 124 after adding 1.

2. Input: [9, 9, 9]
   Output: [1, 0, 0, 0]
   Explanation: The number 999 becomes 1000 after adding 1.

3. Input: [0]
   Output: [1]
   Explanation: The number 0 becomes 1 after adding 1.

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