LeetCode Top Interview 150

66. Plus One

Easy

You are given a large integer represented as an integer array digits, where each digits[i] is the ith digit of the integer. The digits are ordered from most significant to least significant in left-to-right order. The large integer does not contain any leading 0’s.

Increment the large integer by one and return the resulting array of digits.

Example 1:

Input: digits = [1,2,3]

Output: [1,2,4]

Explanation: The array represents the integer 123. Incrementing by one gives 123 + 1 = 124. Thus, the result should be [1,2,4].

Example 2:

Input: digits = [4,3,2,1]

Output: [4,3,2,2]

Explanation: The array represents the integer 4321. Incrementing by one gives 4321 + 1 = 4322. Thus, the result should be [4,3,2,2].

Example 3:

Input: digits = [0]

Output: [1]

Explanation: The array represents the integer 0. Incrementing by one gives 0 + 1 = 1. Thus, the result should be [1].

Example 4:

Input: digits = [9]

Output: [1,0]

Explanation: The array represents the integer 9. Incrementing by one gives 9 + 1 = 10. Thus, the result should be [1,0].

Constraints:

• 1 <= digits.length <= 100
• 0 <= digits[i] <= 9
• digits does not contain any leading 0’s.

Solution

from typing import List

class Solution:
    def plusOne(self, digits: List[int]) -> List[int]:
        num = 1
        carry = 0
        for i in range(len(digits) - 1, -1, -1):
            if i == len(digits) - 1:
                sum_val = digits[i] + carry + num
            else:
                sum_val = digits[i] + carry
            carry = sum_val // 10
            digits[i] = sum_val % 10
        if carry != 0:
            ans = [0] * (len(digits) + 1)
            ans[0] = carry
            for i in range(1, len(ans)):
                ans[i] = digits[i - 1]
            return ans
        return digits

This site is open source. Improve this page.