Title: 统计上升四元组(Count Increasing Quadruplets)

[github-actions]

Difficulty: Hard
Tags: 树状数组(Binary Indexed Tree)、数组(Array)、动态规划(Dynamic Programming)、枚举(Enumeration)、前缀和(Prefix Sum)
Link: https://leetcode.com/problems/count-increasing-quadruplets
LinkCN: https://leetcode.cn/problems/count-increasing-quadruplets