Introduction

In this blog post, we will explore how to solve the LeetCode problem "1945" 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 string s consisting of lowercase English letters, and an integer k. Your task is to convert the string into an integer by a special process, and then transform it by summing its digits repeatedly k times. More specifically, perform the following steps: Convert s into an integer by replacing each letter with its position in the alphabet (i.e. replace 'a' with 1, 'b' with 2, ..., 'z' with 26). Transform the integer by replacing it with the sum of its digits. Repeat the transform operation (step 2) k times in total. For example, if s = "zbax" and k = 2, then the resulting integer would be 8 by the following operations: Convert: "zbax" ➝ "(26)(2)(1)(24)" ➝ "262124" ➝ 262124 Transform #1: 262124 ➝ 2 + 6 + 2 + 1 + 2 + 4 ➝ 17 Transform #2: 17 ➝ 1 + 7 ➝ 8 Return the resulting integer after performing the operations described above. Example 1: Input: s = "iiii", k = 1 Output: 36 Explanation: The operations are as follows: - Convert: "iiii" ➝ "(9)(9)(9)(9)" ➝ "9999" ➝ 9999 - Transform #1: 9999 ➝ 9 + 9 + 9 + 9 ➝ 36 Thus the resulting integer is 36. Example 2: Input: s = "leetcode", k = 2 Output: 6 Explanation: The operations are as follows: - Convert: "leetcode" ➝ "(12)(5)(5)(20)(3)(15)(4)(5)" ➝ "12552031545" ➝ 12552031545 - Transform #1: 12552031545 ➝ 1 + 2 + 5 + 5 + 2 + 0 + 3 + 1 + 5 + 4 + 5 ➝ 33 - Transform #2: 33 ➝ 3 + 3 ➝ 6 Thus the resulting integer is 6. Example 3: Input: s = "zbax", k = 2 Output: 8 Constraints: 1 <= s.length <= 100 1 <= k <= 10 s consists of lowercase English letters.

Explanation

• Initial Conversion: Convert the input string s into an initial integer by replacing each character with its corresponding alphabet position (a=1, b=2, ..., z=26).
  • Digit Summation: Implement a function to calculate the sum of digits of an integer.
  • Iterative Transformation: Apply the digit summation operation k times.

• Runtime Complexity: O(N + K), where N is the length of the string s, and K is the given integer.
• Storage Complexity: O(1) - Constant extra space is used.

Code

    def getLucky(s: str, k: int) -> int:
    """
    Converts a string to an integer based on alphabet positions, then repeatedly sums the digits.

    Args:
        s: The input string consisting of lowercase English letters.
        k: The number of times to repeat the digit summation operation.

    Returns:
        The resulting integer after performing the described operations.
    """

    def sum_digits(n: int) -> int:
        """Calculates the sum of the digits of a non-negative integer."""
        sum_val = 0
        while n > 0:
            sum_val += n % 10
            n //= 10
        return sum_val

    initial_integer = ""
    for char in s:
        initial_integer += str(ord(char) - ord('a') + 1)

    num = int(initial_integer)
    for _ in range(k):
        num = sum_digits(num)

    return num