Plus One

plus_one.py

"""
Description:
Given a non-empty array of digits representing a non-negative integer, plus one to the
integer. The digits are stored such that the most significant digit is at the head of
the list, and each element in the array contain a single digit. You may assume the
integer does not contain any leading zero, except the number 0 itself.

Examples:
Input: [1,2,3]
Output: [1,2,4]

Input: [4,3,2,1]
Output: [4,3,2,2]

Input: [8,9,9,9]
Output: [9,0,0,0]
"""

def plusOne(digits):
    """
    :type digits: List[int]
    :rtype: List[int]
    """
    carry = 0
    digits[-1] += 1
    for i in range(len(digits)-1, -1, -1):
        (carry, rem) = divmod(carry + digits[i], 10)
        digits[i] = rem
        if carry == 0: return digits
    if carry == 1:
        return [1] + [0]*len(digits)