C++ Python公式推導Prefix sum解Leetcode 1685 Sum of Absolute Differences in a...

C++ Python公式推導Prefix sum解Leetcode 1685  Sum of Absolute Differences in a Sorted Array

對於會用Σ處理公式的，Leetcode 1685. Sum of Absolute Differences in a Sorted Array這應算是Bill Gates口中簡單的數學，然後Prefix sum的技巧，O(n)時間能一百趴的解就成形了

[codes on Leetcode]https://leetcode.com/problems/sum-of-absolute-differences-in-a-sorted-array/solutions/4326482/c-python-math-sum-50ms-beats-100/

[Leetcode playList]https://www.youtube.com/watch?v=0iFR8nafMWE&list=PLYRlUBnWnd5IdDHk2BjqXwesydU17z_xk