Leetcode 1432. Max Difference You Can Get From Changing an Integer

Given an integer, you may independently replace all occurrences of one digit with another (for each of two results) and must produce two valid non-zero integers with no leading zeros; return the maximum possible difference between them. The core challenge is picking the digit substitutions that greedily maximize one result (e.g., turning digits to 9) and minimize the other (while avoiding invalid leading zeros).