Introduction

In this blog post, we will explore how to solve the LeetCode problem "1323" 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 num consisting only of digits 6 and 9. Return the maximum number you can get by changing at most one digit (6 becomes 9, and 9 becomes 6). Example 1: Input: num = 9669 Output: 9969 Explanation: Changing the first digit results in 6669. Changing the second digit results in 9969. Changing the third digit results in 9699. Changing the fourth digit results in 9666. The maximum number is 9969. Example 2: Input: num = 9996 Output: 9999 Explanation: Changing the last digit 6 to 9 results in the maximum number. Example 3: Input: num = 9999 Output: 9999 Explanation: It is better not to apply any change. Constraints: 1 <= num <= 104 num consists of only 6 and 9 digits.

Explanation

Here's the solution:

• Find the First 6: The core idea is to iterate through the digits of the number and find the first occurrence of the digit '6'.
• Change to 9: If a '6' is found, change it to '9' to maximize the number.

• Return: Return the modified number (or the original if no '6' was found).

• Runtime Complexity: O(n), where n is the number of digits in num. Storage Complexity: O(1)

Code

    def maximum69Number (num: int) -> int:
    s = str(num)
    s = s.replace('6', '9', 1)
    return int(s)