from collections import deque


def _add_one(nums):
    """Add one to nums."""

    nums = deque(nums)
    n = len(nums)
    carry = 1
    for i in reversed(range(n)):
        add = carry + int(nums[i])
        carry, nums[i] = add // 10, str(add % 10)
    
    if carry:
        nums.appendleft(str(carry))
    
    return list(nums)