Permutation Value Complete Solution

This article is part of the Scaler Topics Fortnightly Contest - 20

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Solution Approach

No matter how you arrange the permutation, the value of f(B) cannot go beyond the product of 2 last two values in the array.

This is because let's say the last 3 values of the permutation be a,b,c with b=n-1 and c=n. If a>=b, the value becomes (n-1)n, else, the value becomes a(n-1).
So the answer will be n*(n-1).
Don't forget to take care of the data type as the answer will overflow in integer data type.

Time Complexity - O(1) Space Complexity - O(1)