Given an array nums, we call (i, j) an important reverse pair if i < j and nums[i] > 2*nums[j].
You need to return the number of important reverse pairs in the given array.
Example1:
Input: [1,3,2,3,1] Output: 2
Example2:
Input: [2,4,3,5,1] Output: 3
Note:
- The length of the given array will not exceed
50,000. - All the numbers in the input array are in the range of 32-bit integer.