1432. Max Difference You Can Get From Changing an Integer

You are given an integer num. You will apply the following steps to num two separate times:

• Pick a digit x (0 <= x <= 9).
• Pick another digit y (0 <= y <= 9). Note y can be equal to x.
• Replace all the occurrences of x in the decimal representation of num by y.

Let a and b be the two results from applying the operation to num independently.

Return the max difference between a and b.

Note that neither a nor b may have any leading zeros, and must not be 0.

Example 1:

Input: num = 555
Output: 888
Explanation: The first time pick x = 5 and y = 9 and store the new integer in a.
The second time pick x = 5 and y = 1 and store the new integer in b.
We have now a = 999 and b = 111 and max difference = 888

Example 2:

Input: num = 9
Output: 8
Explanation: The first time pick x = 9 and y = 9 and store the new integer in a.
The second time pick x = 9 and y = 1 and store the new integer in b.
We have now a = 9 and b = 1 and max difference = 8

Constraints:

• 1 <= num <= 108