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 andnums[i] > 2 * nums[j].\n
Example 1:
\n\n\nInput: nums = [1,3,2,3,1]\nOutput: 2\nExplanation: The reverse pairs are:\n(1, 4) --> nums[1] = 3, nums[4] = 1, 3 > 2 * 1\n(3, 4) --> nums[3] = 3, nums[4] = 1, 3 > 2 * 1\n\n\n
Example 2:
\n\n\nInput: nums = [2,4,3,5,1]\nOutput: 3\nExplanation: The reverse pairs are:\n(1, 4) --> nums[1] = 4, nums[4] = 1, 4 > 2 * 1\n(2, 4) --> nums[2] = 3, nums[4] = 1, 3 > 2 * 1\n(3, 4) --> nums[3] = 5, nums[4] = 1, 5 > 2 * 1\n\n\n
\n
Constraints:
\n\n1 <= nums.length <= 5 * 104-231 <= nums[i] <= 231 - 1给定一个数组 nums ，如果 i < j 且 nums[i] > 2*nums[j] 我们就将 (i, j) 称作一个重要翻转对。
你需要返回给定数组中的重要翻转对的数量。
\n\n示例 1:
\n\n\n输入: [1,3,2,3,1]\n输出: 2\n\n\n
示例 2:
\n\n\n输入: [2,4,3,5,1]\n输出: 3\n\n\n
注意:
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