Watch 10 video solutions for Reverse Pairs, a hard level problem involving Array, Binary Search, Divide and Conquer. This walkthrough by Ashish Pratap Singh has 1,002,125 views views. Want to try solving it yourself? Practice on FleetCode or read the detailed text solution.
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].
Example 1:
Input: nums = [1,3,2,3,1] Output: 2 Explanation: The reverse pairs are: (1, 4) --> nums[1] = 3, nums[4] = 1, 3 > 2 * 1 (3, 4) --> nums[3] = 3, nums[4] = 1, 3 > 2 * 1
Example 2:
Input: nums = [2,4,3,5,1] Output: 3 Explanation: The reverse pairs are: (1, 4) --> nums[1] = 4, nums[4] = 1, 4 > 2 * 1 (2, 4) --> nums[2] = 3, nums[4] = 1, 3 > 2 * 1 (3, 4) --> nums[3] = 5, nums[4] = 1, 5 > 2 * 1
Constraints:
1 <= nums.length <= 5 * 104-231 <= nums[i] <= 231 - 1