give integer array num return number reverse pair arraya reverse pair pair j where0 j numslength andnumsi 2 numsj Example 1input num 13231output 2explanation the reverse pair are1 4 nums1 3 nums4 1 3 2 13 4 nums3 3 nums4 1 3 2 1example 2input num 24351output 3explanation the reverse pair are1 4 nums1 4 nums4 1 4 2 12 4 nums2 3 nums4 1 3 2 13 4 nums3 5 nums4 1 5 2 1 constraints1 numslength 5 104231 numsi 231 1