RotateFunction.java

package easy;

//F(k) = 0 * Bk[0] + 1 * Bk[1] + ... + (n-1) * Bk[n-1]
public class RotateFunction {
    public int maxRotateFunction(int[] A) {
        if(A == null || A.length == 0) return 0;
        int[] F = new int[A.length];
        int[] B = A;
        int max = Integer.MIN_VALUE;
        for(int i = 0; i < A.length; i++){
            F[i] = compute(B);
            max = Math.max(max, F[i]);
            B = rotate(B);
        }
        return max;
    }

    private int compute(int[] b) {
        int sum = 0;
        for(int i = 0; i < b.length; i++){
            sum += i*b[i];
        }
        return sum;
    }

    private int[] rotate(int[] a) {
        int first = a[0];
        for(int i = 1; i < a.length; i++){
            a[i-1] = a[i];
        }
        a[a.length-1] = first;
        return a;
    }
    
    public static void main(String...strings){
        int[] nums = new int[]{4, 3, 2, 6};
        RotateFunction test = new RotateFunction();
        System.out.println(test.maxRotateFunction(nums));
    }
}