Java implementation LeetCode 396 rotate function

396. rotation function

Given an array of integers of length n A.

Bk is assumed that the rotation of the array A k array positions clockwise "rotation function" F we define A as:

F(k) = 0 * Bk[0] + 1 * Bk[1] + … + (n-1) * Bk[n-1]。

Calculating F (0), F (1), ..., F (n-1) of the maximum value.

Note:
can be considered the value of n is less than 105.

Example:

A = [4, 3, 2, 6]

F(0) = (0 * 4) + (1 * 3) + (2 * 2) + (3 * 6) = 0 + 3 + 4 + 18 = 25
F(1) = (0 * 6) + (1 * 4) + (2 * 3) + (3 * 2) = 0 + 4 + 6 + 6 = 16
F(2) = (0 * 2) + (1 * 6) + (2 * 4) + (3 * 3) = 0 + 6 + 8 + 9 = 23
F(3) = (0 * 3) + (1 * 2) + (2 * 6) + (3 * 4) = 0 + 2 + 12 + 12 = 26

Therefore, F (0), the maximum value in (3) F (1), F (2), F is F (3) = 26.

class Solution {
     public int maxRotateFunction(int[] A) {
        int allSum =0;
        int len = A.length;
        int F=0;
        for(int i=0; i<len; i++){
            F+=i*A[i];
            allSum += A[i];
        }
        int max=F;
        for(int i=len-1; i>=1; i--){
            F = F +allSum - len*A[i];
            max = Math.max(F, max);
        }
        return max;
    }
}