Introduction

In this blog post, we will explore how to solve the LeetCode problem "2544" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like Chatmagic, we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

Problem Statement

You are given a positive integer n. Each digit of n has a sign according to the following rules: The most significant digit is assigned a positive sign. Each other digit has an opposite sign to its adjacent digits. Return the sum of all digits with their corresponding sign. Example 1: Input: n = 521 Output: 4 Explanation: (+5) + (-2) + (+1) = 4. Example 2: Input: n = 111 Output: 1 Explanation: (+1) + (-1) + (+1) = 1. Example 3: Input: n = 886996 Output: 0 Explanation: (+8) + (-8) + (+6) + (-9) + (+9) + (-6) = 0. Constraints: 1 <= n <= 109

Explanation

Here's an efficient solution to the problem:

• Convert to String and Iterate: Convert the integer n into a string to easily access its digits. Iterate through the digits of the string.
• Alternating Signs: Maintain a sign variable that alternates between 1 and -1 for each digit. Multiply each digit (converted to an integer) by the current sign and add it to the total.

• Update Sign: After processing each digit, flip the sign for the next digit.

• Runtime Complexity: O(log n), where n is the input integer (due to the number of digits). Storage Complexity: O(log n) in the worst case to store the string representation of the number, but can be optimized to O(1) by directly extracting the digits.

Code

    def alternate_digit_sum(n: int) -> int:
    """
    Calculates the sum of digits of a number with alternating signs.

    Args:
        n: The input positive integer.

    Returns:
        The sum of the digits with alternating signs.
    """
    n_str = str(n)
    total = 0
    sign = 1
    for digit in n_str:
        total += sign * int(digit)
        sign *= -1
    return total