Count Number of Pairs With Absolute Difference K — LeetCode 2006 Python Solution

The problem

Given an integer array nums and an integer k, return the number of pairs (i, j) where i < j such that |nums[i] - nums[j]| == k. The value of |x| is defined as: x if x >= 0.

Example

Input

nums = [1,2,2,1], k = 1

Output

4

Explanation

The pairs with an absolute difference of 1 are:

Python solution

class Solution:
    def countKDifference(self, nums: List[int], k: int) -> int:
        n = len(nums)
        return sum(
            abs(nums[i] - nums[j]) == k for i in range(n) for j in range(i + 1, n)
        )

Complexity

Pattern: Hash Map

Trade memory for time: remember what you have seen so the second pass never happens. LeetCode 2006. Count Number of Pairs With Absolute Difference K is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Hash Table and Counting.

The hash map guide has the Python template for the pattern and the 709 LeetCode problems that use it.

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