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Java Solution for LeetCode algorithm problems, continually updating
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493\. Reverse Pairs
Hard
Given an integer array `nums`, return _the number of **reverse pairs** in the array_.
A reverse pair is a pair `(i, j)` where `0 <= i < j < nums.length` and `nums[i] > 2 * nums[j]`.
**Example 1:**
**Input:** nums = [1,3,2,3,1]
**Output:** 2
**Example 2:**
**Input:** nums = [2,4,3,5,1]
**Output:** 3
**Constraints:**
* 1 <= nums.length <= 5 * 104
* -231 <= nums[i] <= 231 - 1