每日一题 2006. 差的绝对值为 K 的数对数目

class Solution:
    def countKDifference(self, nums: List[int], k: int) -> int:
        cnt = 0
        for i in range(len(nums)):
            for j in range(i+1,len(nums)):
                if abs(nums[j]-nums[i]) == k:
                    cnt += 1
        return cnt

class Solution:
    def countKDifference(self, nums: List[int], k: int) -> int:
        cnt, ans = Counter(nums), 0
        for key in cnt:
            if (key + k) in cnt:
                ans += cnt[key] * cnt[key + k]                
        return ans