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

Solution: O(N log N) Given two sorted arrays A[] and B[] it is quite easy to see for every