menu

[LeetCode] 066. Plus One

Problem (Easy)

066. Plus One

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.

Example 1:

  • Input: [1,2,3]
  • Output: [1,2,4]
  • Explanation: The array represents the integer 123.

Example 2:

  • Input: [4,3,2,1]
  • Output: [4,3,2,2]
  • Explanation: The array represents the integer 4321.

Approach 1: (My Solution - String Operations)

Idea

Use string operations to do the work.

Solution

class Solution1:
    def plusOne(self, digits):
        """
        :type digits: List[int]
        :rtype: List[int]
        """
        plus = int(''.join([str(i) for i in digits])) + 1
        return [int(i) for i in list(str(plus))]

Complexity

  • Time: $O(n)$
  • Space: $O(n)$

Approach 2: (My Solution - Without String Operation)

Idea

Loop number by number.

Solution

class Solution2:
    def plusOne(self, digits):
        """
        :type digits: List[int]
        :rtype: List[int]
        """
        inc = 1
        for i in range(len(digits)):
            inc, digits[-1-i] = divmod(digits[-1-i]+inc, 10)
        if inc:
            digits = [1] + digits
        return digits

Complexity

  • Time: $O(n)$
  • Space: $O(1)$



KF

Comments