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Quiz

#1432 Max Difference You Can Get From Changing an Integer

APPROACH

An integer num is given. Twice independently, perform the following procedure: choose a source digit x (0 <= x <= 9) and a replacement digit y (0 <= y <= 9), then substitute every occurrence of x in num's decimal representation with y. Call the two resulting integers a and b.

Return the maximum possible value of a - b.

Neither a nor b may contain leading zeros, and neither may equal zero.

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

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What is the optimal approach for this problem?