[untitled] leetcode 396 rotation function [finding laws in mathematics] the way of leetcode in heroding

Their thinking ：
A very simple mathematical logic reasoning problem , Simply put, it's about finding rules , Every two consecutive F Subtracting the , There will always be F(i)-F(i-1)=sum+n*nums[n-i], So according to this Law , Just put F(0) Work it out , The back ones come out directly , There's no need for violence , The code is as follows ：

class Solution {
    
public:
    int maxRotateFunction(vector<int>& nums) {
    
        int n = nums.size();
        int sum = 0, F = 0;
        for(int i = 0; i < n; i ++) {
    
            sum += nums[i];
            F += i * nums[i];
        }
        int maxSum = F;
        for(int i = 1; i < n; i ++) {
    
            F = F + sum - n * nums[n - i];
            maxSum = max(maxSum, F);
        }
        return maxSum;
    }
};