LeetCode-Python/plus_one.py at main · Mickey0521/LeetCode-Python · GitHub

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class Solution:
    def plusOne(self, digits: List[int]) -> List[int]:

        # plus one
        carry_digit = 0
        digits[len(digits)-1] = digits[len(digits)-1] + 1

        # for loop (start from the last one)
        for index in range( len(digits)-1, -1, -1):

            # add the carry_digit
            digits[index] = digits[index] + carry_digit

            if digits[index] == 10:
                digits[index] = 0
                carry_digit = 1
            else:
                digits[index] = digits[index]
                carry_digit = 0

        # handle the edge case:
        # append integer to the beginning of the list
        if carry_digit == 1:
            digits.insert(0, 1) # insert(index, value)

        return digits