Number of Excellent Pairs — LeetCode 2354 Python Solution

The problem

You are given a 0-indexed positive integer array nums and a positive integer k. A pair of numbers (num1, num2) is called excellent if the following conditions are satisfied: Both the numbers num1 and num2 exist in the array nums.

Example

Input

nums = [1,2,3,1], k = 3

Output

5

Explanation

The excellent pairs are the following:

Python solution

class Solution:
    def countExcellentPairs(self, nums: List[int], k: int) -> int:
        s = set(nums)
        ans = 0
        cnt = Counter()
        for v in s:
            cnt[v.bit_count()] += 1
        for v in s:
            t = v.bit_count()
            for i, x in cnt.items():
                if t + i >= k:
                    ans += x
        return ans

Complexity

Pattern: Bit Manipulation

Use XOR, masks and the low-bit trick to replace whole data structures with an integer. LeetCode 2354. Number of Excellent Pairs is filed here because LeetCode tags it Bit Manipulation, which is the vocabulary this hub collects.

The bit manipulation guide has the Python template for the pattern and the 194 LeetCode problems that use it.

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