You can find the problem there 1930F - Maximize the Difference.

Before you continue the reading, this is my first blog, I don't know how to write mathematical formulas with codeforces, as for example maximum over a set. If any advice for this it will be helpful.

Problem statement

Given an array b of m non-negative integers, we must calculate f(b) as the maximum value of max(bi|x)−min(bi|x) over all possible non-negative integers x.

And as hints, the editorial mention :

1. For an array b consiting of m non-negative integers, f(b)=max(max(bi|bp)−min(bi|bp))

2. f(b) is the maximum value of bi ∧ ~ bj over all pairs

If you have any solution feel free to comment on it. Thanks!!!