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Problem: Reverse Pairs

Medium
30 min
Explore how to identify and count reverse pairs in arrays by applying sorting combined with binary search or two-pointer methods. This lesson helps you understand problem constraints, implement solutions in code, and develop mastery in sorting and search patterns that improve coding interview skills.

Statement

You are given an integer array, nums. Your task is to count how many reverse pairs exist in the array and return the total number of such pairs.

A reverse pair is defined as a pair of indexes (i,j)(i, j) such that:

  • 0≤i<j<0 \leq i \lt j \lt nums.length, and

  • nums[i] >2×\gt 2 \times nums[j].

Constraints:

  • 1≤1 \leq nums.length ≤5×104\leq 5 \times 10^4

  • −231≤-2^{31} \leq nums[i] ≤231−1\leq 2^{31} - 1

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Problem
Ask
Submissions

Problem: Reverse Pairs

Medium
30 min
Explore how to identify and count reverse pairs in arrays by applying sorting combined with binary search or two-pointer methods. This lesson helps you understand problem constraints, implement solutions in code, and develop mastery in sorting and search patterns that improve coding interview skills.

Statement

You are given an integer array, nums. Your task is to count how many reverse pairs exist in the array and return the total number of such pairs.

A reverse pair is defined as a pair of indexes (i,j)(i, j) such that:

  • 0≤i<j<0 \leq i \lt j \lt nums.length, and

  • nums[i] >2×\gt 2 \times nums[j].

Constraints:

  • 1≤1 \leq nums.length ≤5×104\leq 5 \times 10^4

  • −231≤-2^{31} \leq nums[i] ≤231−1\leq 2^{31} - 1

Similar Problems
Two Sum Less Than K
Valid Triangle Number
Count Pairs in Two Arrays
Put Marbles in Bags
H-Index
Sum of Mutated Array Closest to Target
Contains Duplicate II
Find K-th Smallest Pair Distance
Maximum Number of Integers to Choose from a Range I
Find the Distance Value Between Two Arrays